I JO ro M ; a o N CÖ Ü •»-I ce g. a a Volume 20 Number 3 September 1996 ISSN 0350-5596 Informatica An International Journal of Computing and Informatics Profile: S. Alagic Fuzzy Modal Logic for Information Retrieva Limitations of Intelligent Systems Another Look at Computability Journal of Consciousness Studies The Slovene Society Informatika, Ljubljana, Slovenia \ r,: F Informatica An International Journal of Computing and Informatics < Basic info about Informatica and back issues may be FTP'ed from ftp. arnes. si in magazines/informatica ID: anonymous PASSWORD: FTP archive may be also accessed with WWW (worldwide web) clients with r'; URL: http://www2.ijs.si/~mezi/inforinatica.html f ' Subscription Information Informatica (ISSN 0350-5596) is published four times a year in , 3 Spring, Summer, Autumn, and Winter (4 issues per year) by the Slovene Society Informatika, I • Vožarski pot 12, 610Ò0 Ljubljana, Slovenia. * ■ The subscription rate for 1996 (Volume 20) is - DEM 50 (US$ 35) for institutions, - DEM 25 (US$ 17) for individuals, and ^ - DEM 10 (US$ 7) for students '] plus the mail charge DEM 10 (US$ 7). 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PROFILES This issue of Informatica presents a profile of Professor Suad Alagić, a computer science researcher and educator of international reputation. He was born in Bosnia, and accomplished much of his professional success working at the University of Sarajevo. Suad Alagić has been a member of the Editorial Board of Informatica since 1988 when the younger generation of the Yugoslav computer scientists came to the professional surface. That made it possible for Informatica to pursue a course toward becoming an international journal. At that time Suad Alagić was already the most distinguished "computer scientist" (in the traditional-sense of the word) not only in Bosnia & Herzegovina, but in the former Yugoslavia as well. Suad Alagic's international publishing activity, research, and lecturing work has been closely connected with Springer-Verlag, the publisher of three of his books (The Design of Well-Structured and Correct Programs, Relational Database Technology and Object-Oriented Database Programming). He also published in major international Computer Science journals such as Journal of Computer and System Sciences, Information Systems Journal, Computer Journal, Acta Informatica, Transactions on Information and Systems, and Theoretical Computer Science. He had numerous papers at international conferences. Many of them have been published in Springer's Lecture Notes in Computer Science. He has had research grants from NSF, U.S. Department of Defense, and industry. His biographical sketch appeared in several recent editions of Marquis Who's Who in the World, Who's Who in Science and Engineering, and Who's Who in Finance and Industry. His Ph.D. work at the University of Massachusetts under supervision of Professor Arbib had a decisive influence on his career. Michael A. Arbib was one of the most influential computer scientists in the world at that time. The type of education and exposure that Suad Alagić had while at the University of Massachusetts made it possible for him to meet for many years the highest professional standards of Computer Science excellence. The reader will find plenty of evidence for these strong statements in the references in the curriculum vitae that follows. I (the Editor of this profile) can speak about Suad Alagić international standing from my personal experience based on my visit to Japan in 1985^. When I visited the Institute for New Generation Computer Technology—ICOT (Mita Ku-sakai Building in Tokyo, on November 11, 1985), Dr. K. Furukawa, the vice president, told me that I am the second person from Yugoslavia to whom permission for visiting ICOT was given: the first one was Suad Alagić. At that time the restrictions for a visit to ICOT were really rigorous, especially for visitors of the Eastern European countries. But Alagić's book "The Design of Well-Structured and Correct Programs" (co-authored with M.A. Arbib) was already translated into Japanese, and in wide use at Japanese universities. But along with his professional achievements and international recognition Suad Alagić belongs to those rare researchers and scholars in Computer Science who experienced the drama of the civil war in the former Yugoslavia. In the war Suad Alagić lost almost everything he worked for many years of professional activity in Sarajevo. Suad Alagić was a professor at the University in Sarajevo, where he lectured on some of the most propulsive fields of computer science at that time (databases, programming languages and programming methodology). He held several important positions at his university, most notably those of Chair of the Department of Computer Science and Informatics, and Pro-rector for Science and Technology of the University of Sarajevo. When the civil war in the former Yugoslavia finally moved to Bosnia & Herzegovina, Suad Alagić was on a visiting appointment at the University of Vermont. His wife and their two children were with him as well. This was an exceptionally fortunate accident. They did not expect the tragedy that subsequently happened in their home city. They suffered the loss of everything they had in their home in the Sarajevo suburb of Grbavica. The same unfortunate destiny was shared by Suad's department in Sarajevo. His parents, his sister, and his closest friends survived the tragedy. 'The aim and the success of the visit was exhaustively described in A.P. Železnikar: From Sapporo to Tokyo, Back to Ljubljana. Informatica 10 No. 2: 68-74 (in Slovene). Although Suad Alagić and his closest family were not in Sarajevo during the war, the experience of helplessly watching the destruction of Sarajevo on the American television was deeply traumatic for him and his family. Those traumas are not likely to ever go away. The resume that follows provides information on how Suad Alagić continued his successful career in the United States, while hoping be able to provide in the near future yet another contribution to the academic life in his field in Sarajevo. The profile of Professor Suad Alagić which follows is dedicated to the memory of the circumstances in which this unusual individual worked and contributed to the core of Computer Science. Our hope is that such individual careers will again be possible in the Balkans after a period of peaceful hfe and cooperation of closely related cultures and neighbors. Current Position Professor, Department of Computer Science, Wichita State University, Wichita, Kansas 672600083. Phone: (316) 689 3916. Email: alagic@cs.twsu.edu. Research Areas Object-Oriented Systems, Database Systems, and Programming Languages and Systems. Education: — Postdoctoral Fellow: Department of Computer Science, University of Edinburgh, 1977. — Ph.D.-. Department of Computer and Information Science, University of Massachusetts at Amherst, 1974. — M.Sc.: Department of Computer and Information Science, University of Massachusetts at Amherst, 1972. — B.Sc.: Diploma in Electrical Engineering, Department of Control Systems, Faculty of Electrical Engineering, University of Sarajevo, 1970. Books: — S. Alagić: Object-Oriented Database Programming. Springer-Verlag. New York, 1988. — S. Alagić: Relational Database Technology. Springer-Verlag. New York, 1986. — S.Alagić & M.A. Arbib: The Design of Well-Structured and Correct Programs. SpringerVerlag. New York, 1978, 1980. Translations: Japanese (1980), Russian (1984), Polish (1983). Papers published in: — Journal of Computer and Systems Sciences, — Information Systems Journal, — Computer Journal, — Acta Informatica, — Transactions on Information and Systems, — Theoretical Computer Science, — Lecture Notes in Computer Science, etc. Grants from D OD, NSF and industry. Biographical sketch in recent editions of: — Marquis Who's Who in the World. — Marquis Who's Who in Science and Engineering. — Marquis Who's Who in Finance and Industry. Academic Career: —1993-... : Professor. Department of Computer Science. Wichita State University. -1995, 1996: Faculty Fellow. National Institute for Aviation Research. — 1993-1994: Chair. Department of Computer Science. Wichita State University. — 1991-1993: Visiting Faculty. Department of Computer Science and Electrical Engineering. University of Vermont. — 1986-1991: Professor. Department of Computer Science and Informatics. ETF—Faculty of Electrical Engineering. University of Sarajevo. -1989-1991: Chairman of ETF. — 1989-1991: Vice-Rector for Science and Technology. University of Sarajevo. — 1985: Visiting Researcher. Department of Information Science and Electronics. University of Tsukuba, Japan. -1983-1987: Research Associate. Institute of Computer and Control Systems, Sarajevo. — 1980-1986: Associate Professor. — 1975-1980: Assistant Professor. Department of Computer Science and Informatics. ETF— Faculty of Electrical Engineering. University of Sarajevo. — 1977: Postdoctoral Fellow. Department of Computer Science. University of Edinburgh. -1971-1974: Graduate Research Assistant. Department of Computer and Information Science. University of Massachusetts at Amherst. Research — Object-Oriented Databfise Technology and Database Programming Languages The initial research in the area of the object-oriented database technology was mainly related to the design and implementation of Modulex, a database programming environment supporting multiple paradigms (object-oriented and relational in particular). The associated pubHcations are the book Object-Oriented Database Programming and the papers Object-Oriented Database Programming Environment Based on Modula-2, Persistent Meta-Objects and Toward Multipara-digm Database Interfaces. AppHcations of the developed technology have been in the area of production management systems and spatial data management with the associated publications: Object-Oriented Geo-Information Processing in Modulex and Advanced Database Programming Languages: A Geo-Information Processing Prospective. — Database Type Systems The follow-up research was largely devoted to further developments of the strongly typed database technology with the goal to introduce high-degrees of polymorphism, a sophisticated meta-level support, polymorphic facilities based on kinds (of types), higher-order polymorphism and reflection. The associated publications, are: Generic Modules, Kinds and Polymorphism for Modula-2, Joins as Fullbacks, Polymorphic and Reflective Type Structures, tutorial publication: Objects, Modules, Kinds and Reflection in Database Programming Environments, Integrating Inheritance, Subtype and Parametric Polymorphism in Database Type Systems, Object-oriented Type Evolution Using Reflection, TypeSafe Linguistic Reflection: A Generator Technology, Polymorphic and Reflective Type Structures, Duality in Object-Oriented Type Systems, Inheritance Versus Subtyping: Conflict or Duality and F-bounded Polymorphism for Database Programming Languages. An overview of the key issues in these papers is presented in the tutorial Object-Oriented Type Systems. — Typed Logic-Based Object-Oriented Technology Further developments are reflected in the most recent collection of papers (Declarative Object-Oriented Programming: Inheritance, Subtyping and Prototyping, A Typed Object-Oriented Database Technology with Deductive and Reflective Capabilities, Expressibility of Typed Logic Paradigms for Object-Oriented Databases, Typed Declarative Object-Oriented Database Programming, A Temporal Object-Oriented Language System with Logic-based Executable Specifications, A Typed and Temporal Object-Oriented Database Technology). These papers deal with a logic-based, typed object-oriented technology. A variety of logic paradigms are explored as a basis for declarative object-oriented languages, prototyping tools and a strongly typed object-oriented database technology. — Relational Database Technology The work on the integration of database and programming languages and systems (Relational Pascal Database Interface, Relational Pascal Database Programming Environment, Relational Pascal Model of Soil Database) produced a complete, relational, strongly typed, multi-user database programming environment including a highlevel, non-procedural definition, query, manipulation and control language, transaction support, dynamic indices, concurrency control and reco- very. The system was in actual commercial use at some ten sites. The research visit to Japan included presentation of the above work in a number of research institutions involved in the projects of the new generation of computer systems (ETL (Elec-trotechnical Laboratory), Tokyo University, Tsu-kuba University, NEC Research Laboratory, Hitachi Systems Laboratory, NTT Computer and Communications Laboratory) as well as a visit to ICOT (Tokyo Institute for the New Generation of Computer Systems). The integration of the major published results on the relational database technology together with the results in developing a specific, strongly typed relational database technology in the quoted research and development projects have been presented in the book Relational Database Technology. — Programming Languages and Programming Methodology Most recent results are in the area of declarative and temporal object-oriented programming, reflected in recent submissions (A Temporal Constraint System for Object-Oriented Databases, Temporal Object-Oriented Programming). But the deepest recent formal results are on the model theory of a temporal constraint language (Order-Sorted Model Theory for Temporal Executable Specifications). Earlier work, starting with the Ph.D. dissertation (Algebraic Aspects of Programming and Formal Languages) and the follow-up papers (Natural State Transformations, Categorical Theory of Tree Processing) dealt with the categorical approach to some problems in formal language theory .(tree transformations) and programming languages (abstract data types). The first book co-authored with Michael A. Ar-bib (The Design of Well-Structured and Correct Programs) and related papers (such as Proof Rules for Gotos with M. A. Arbib) belong to the area of programming methodology based on the axiomatic approach (Hoare's logic) and formal verification of program correctness. The research visit to Edinburgh was largely devoted to the related problems. Grants — DOD (Army Research Office) Research Grant (1996-1999): A Typed and Temporal Object-Oriented Technology. — DOD Defense University Research Instrumentation Grant (1994-1995): Integrated Object-Oriented Environment for Modeling-, Simulation, Prototyping and Active Databases. — NSF Research Grant: Extended Relational Database Programming Environment. — USA-Yugoslav Joint Board for Scientific and Technological Co-operation; Industrial Grant: Design and Implementation of a Relational Database Management System for a 32-bit Microcomputer. — Research grants —Scientific Community of Bosnia and Herzegovina: Relational Pascal Database Management System; Conceptual Modeling; Relational Technology in Production Management Systems; New Database Technologies; Information Technologies; and Mathematical Aspects of Programming Languages. Recent Lab Development Work Object-Oriented Research Lab, DOD Grant, 1994-1995. This is a lab based on SUN, SGI and NCD equipment running a variety of object-oriented systems (C-|—I- and Eiffel compilers, two object-oriented database management systems (ODE and 02) and one object-oriented storage manager (BESS)). International Consulting — Environmental Databases Most of it has been done for UNEP —United Nations Environment Program in the capacity of a database expert for the following UNEP projects: GRID—General Resource Information Database (London, England; Nairobi, Kenya; and Geneva, Switzerland). MAP—Integrated Data System for the Mediterranean Action Plan (Athens, Greece; Sophia Antipolis, Prance; and La Valleta, Malta). HEM—^Harmonization of Environmental Measurements Design of the HEM Metadatabase (Munich, Germany). The technical problems involved belong to the design of large scale databases (and their metadata-bases) with non-standard types (spatial and temporal). Teaching Activities Undergraduate courses taught: Object-Oriented Programming in C++; Introduction to Database Technology; Programming Languages, Concepts of Programming Languages; Database Design, Data Structures; Systems Programming, Programming Methodology; Theory of Algorithms and Automata; and Mathematical Foundation of Computer and Information Science. Graduate courses taught: Object-Oriented Systems, Object-Oriented Databases, Advanced Topics in Database Systems, Compiler Construction, and Relational Database Technology. Ph.D. students: Four of them received their degrees so far. •Theses Ph.D. Dissertation: Algebraic Aspects of Programming and Formal Languages, directed by Michael A. Ar bib. M.Sc. Project: Semantics of Algorithmic Languages, directed by Michael A. Arbib. B.Sc. Diploma Thesis: Regular Languages. Recent Program Committee Memberships Software QuaUty Management, SQM '95, '96. Extending Database Technology, EDBT '88, International Conference, Venice 1988. EDBT 92, International Conference, Vienna 1992 International Workshop on Foundation of Data Models and Languages, Aigen, Austria, 1991. TOOLS 91; Technology of Object-Oriented Languages and Systems, International Conference, Paris, 1991. International Conference on Logical Methods and Tools in Conceptual Design of Information Systems, Nantes, France 1989. Publications Books S. Alagic, Object-Oriented Database Programming, Springer-Verlag, New York, 1988. S. Alagic, Relational Databajse Technology, Springer-Verlag, New York, 1986. S.Alagić, M.A. Arbib, The Design of V^ell-Structured and Correct Programs, SpringerVerlag, New York, 1978, 1980. Translations: Japanese: Kagaku-Gijyutsu, Tokyo, 1980. Russian-: Radio i Svjaz, Moscow, 1984. Polish: Wydawnictawa Naukowo-Technicze, Warsaw, 1983. Selected Papers S. Alagic, A typed and temporal object-oriented database technology, lEICE Transactions on Information and Systems, Vol. 78, 1995. S. Alagic, G. Nagati, J. Hutchinson and D. Ellis, Object-oriented flight simulator technology, Proceedings of AIAA Conference, 1996. S. Alagic and M. Alagic, Order-sorted model theory for temporal executable specifications. Theoretical Computer Science, to appear. S. Alagic, A temporal constraint system for object-oriented databases, Workshop on Con-, straints and Databases, Constraint Programming Conference, 1996. S. Alagic, Flight simulator database: Object- oriented design and implementation. In: A. Chaud-hri and M. Loomis, Object-Oriented Databases (tentative title), to appear. S. Alagic, R. Sunderraman and A. Radiya, A Typed declarative object-oriented database programming, In: V. S. Alagar and R. Missaoui, Object Orientation in Databases and Software Engineering, World Scientific, 1995. S. Alagić, R. Sunderraman and R. Bagai, Declarative object-oriented programming: inheritance, subtyping and prototyping. Proceedings of the . European Conference on Object-Oriented Prò- . gramming - ECOOP '94, Lecture Notes in Com-r, puter Science, Vol. 821, Springer-Verlag, 1994. S. Alagić and R. Sunderraman, Expressibility of typed logic paradigms for object-oriented databases, Proceedings of the 12th British National Database Conference, BNCOD-12, Lecture Notes in Computer Science, Vol. 826, Springer-Verlag, 1994. S. Alagić, R. Sunderraman and R. Bagai, A typed object-oriented database technology with deductive and reflective capabilities, Proceedings of the International Symposium on Advanced Database Technologies and Their Integration, ADTI '94, Nara, Japan, 1994. M. Surendhar and S. Alagić, Object-oriented type evolution using reflection. Proceedings of TOOLS EUROPE '94 (Technology of Object-Oriented Languages and Systems), Paris 1994, Prentice-Hall. R. Bagai, S. Alagić and R. Sunderraman, A prototyping technology for typed object-oriented software development, Proceedings of the Second International Conference on Software Quahty Management, Computational Mechanics, Edinburgh, 1994. S. Alagić, F-bounded polymorphism for database programming languages. Proceedings of the Second East/West Database Workshop, Linz, Austria, Workshops in Computing, Springer-Verlag, 1994. S. Alagić and A. Radiya, A temporal object-oriented language system with logic-based executable specifications, ECOOP 1994 Workshop: Logical Foundations of Object-Oriented Programming, 1994. S. Alagić, Duality in object-oriented type systems (abstract). Proceedings of the Workshop on Combining Declarative and Object-Oriented Databases, Washington, D.C., 1993. S. Alagić and D. Stemple, Inheritance versus subtyping: conflict or duality (abstract). The Fourth International Workshop on Database Programming Languages, New York, 1993. S. Alagić, Algol 68. A.Ralston and E.D. Reilly (eds.): Encyclopedia of Computer Science, Van Nostrand Reinhold, New York, 1976. Second edition 1984. Third edition 1993. S. Alagić, Polymorphic algorithms for strongly typed relational database operators (abstract), Midwestern Conference on Combinatorics, Cryptography and Computing, 1993. S. Alagić, Polymorphic and reflective type structures. Proceedings of the International Conference on the Technology of Object-Oriented Languages and Systems, TOOLS USA '92, Santa Barbara, 1992. S. Alagić, Integrating inheritance, subtype and parametric polymorphism in database type systems, Proceedings of ICSC '92, Second International Computer Science Conference, Data and Knowledge Engineering: Theory and Practice, Hong Kong, 1992. D. Stemple, R.B. Stanton, T. Sheard, P. Phil-brow, R. Morrison, G.N.C. Kirby, L. Fegaras, R.L. Cooper, R.C.H. Connor, M.P. Atkinson and S. Alagić, Type - safe linguistic reflection: A generator technology, Research Report CS/92/6, Department of Mathematical and Computational Sciences, University of St Andrews, Scotland, 1992. S. Alagić, Persistent metaobjects. In: A. Dearie, G.M. Shaw and S. B. Zdonik (Eds): Implementing Persistent Object Bases: Principles and Practice, Proceedings of the Fourth International Symposium on Persistent Object Systems, Walter Kaufman Publishers, 1991. S. Alagić, Toward multiparadigm database interfaces, In: J.W. Schmidt and A. A. Stogny (eds): Next Generation of Information Systems Technology, Proceedings of the First International East/West Workshop, Kiev, 1990, Lecture Notes in Computer Science, Vol. 503, Springer- Verlag, 1991. S. Alagić, Generic modules, kinds and polymorphism for Modula-2, Proceedings of the Second International Modula-2 Conference, Loughborough, England, 1991. S. Alagić and M. Alagić, Joins as pullbacks. Proceedings of the Third International Workshop on Foundation of Data Models and Languages, Aigen, Austria, 1991. S. Alagić and Z. Galić, Object-oriented geo-information processing in Modulex, TOOLS '90, Technology of Object- Oriented Languages and Systems, Proceedings of the Second International Conference, Paris, 1990. S. Alagić and Z. Galić, Advanced database programming languages: Geo-information processing prospective. Proceedings of CIPS '90, Edmonton, Canada, 1990. S. Alagić, D. Jurković and M. Kandić, Object-oriented database programming environment based on Modula-2, Proceedings of the First Inter- national Modula-2 Conference, 1989. S. Alagić, M. Kandié and N. Krdzalić, Object-oriented versus conventional database methods and tools, Proceedings of the Third International Conference: Pratique des metodes et ou-tils logiciels d'aide a la conception de systemes d'information, Nantes, France, 1989. M. Alagić, S. Alagić, Categorical approach to the relational model of data. Journal Informatica 3/1987, Ljubljana. S. Alagić, Integrated Data System for the Mediterranean Action Plan, United Nations Environment Programme, Athens, 1984. S. Alagić et al.. Relational Pascal model of soil database. Proceeding of the ISS Working Conference on Soil Information Systems Technology, Oslo, 1983, PUDOC, Wageningen, Holland, 1984. S. Alagić, Database Considerations: A Structural View, Report on GEMS, United Nations Environment Program, London 1983. S. Alagić and A. Kulenović, Relational Pascal database interface, The Computer Journal, Vol. 24. Heyden Son,1981. M. A. Arbib, S. Alagić, Proof rules for gotos. Acta Informatica 11, 1979, Springer-Verlag. S. Alagić, On proofs of correctness of well-structured programs, I and IL Journal Matematički Vesnik, Belgrade, Yugoslavia 1978. S. Alagić at al., A hierarchical host language system based on B -trees. Proceedings of the Annual Congress AICA, Pisa, Italy, 1977. S. Alagić, A. Kulenović and M. Sarajlić, Structured extension of Cobol for handling data bases, Information Systems Journal, 1976, Perga-mon Press. S. Alagić, Cleaning up unstructured algorithms using invariants. Journal Informatica, Ljubljana, Yugoslavia, 1977. S. Alagić, Natural state transformations. Journal of Computer and System Sciences, 1975, Academic Press. S. Alagić, Categorical theory of tree processing. Proceedings of the First International Symposium: Category Theory Applied to Computation and Control. San Francisco, 1974, Lecture No- tes in Computer Science, Vol.25, Springer Verlag, 1975. S. Alagić, M. A. Arbib and R. W. Taylor, Algebraic models of syntax, semantics and data structures. Computer and Information Science Technical Report, University of Massachusetts, Amherst 1974. S. Alagić, Algebraic aspects of Algol 68, Computer and Information Science Technical Report 73B-5, University of Massachusetts, Amherst 1973. Recent submissions S. Alagić, Temporal object-oriented programming, submitted to a journal, 1995. Tutorials S. Alagić, Object-Oriented Type Systems, Tutorial, 8th International Conference on the Technology of Object-Oriented Languages and Systems, TOOLS USA '92, Santa Barbara, 1992. S. Alagić, Objects, modules, kinds and reflection in database management systems, TOOLS '91, International Conference: Technology of Object-Oriented Languages and Systems, Paris, 1991 (Invited Seminar: Object-Oriented Databases). Reference manuals S. Alagić et al,, EQUAL: Language Specification and Application Guide, Technical Publication, Institute of Control and Computer Science, Sarajevo, 1985. S. Alagić et al., PASCAL/E: Language Specification and AppHcation Guide, Technical Publication, Institute of Control and Computer Science, Sarajevo, 1985. Other Papers S. Alagić, Categorical analysis of Algol 68, Proceedings of the Symposium Informatica 74, Bled, Yugoslavia, 1974. S. Alagić, Mathematical foundation of programming languages. Proceedings of the Symposium Informatica 74, Yugoslavia, Bled, 1974. S. Alagić, A. Kulenović and M. Sarajlić, A Structured extension of Cobol for handling data bases, Proceedings of the Symposium Informatica, Bled, 1975. S. Alagić, A modest host language system. Proceedings of the Symposium Computer at the University, 1974, Zagreb, Yugoslavia. S. Alagić, Structured programming and program proving. Proceedings of the Symposium Informatica 75, invited paper. Bled, Yugoslavia, 1975. S. Alagić et al.. Implementing hierarchies of sets using B-trees. Proceedings of the Symposium Informatica 77, Bled, 1977. S. Alagić et al., On strategies for implementing data structure sets, Proceedings of the Symposium Informatica 77, Bled, 1977. S. Alagić et al, A relational storage system based on B -trees. Proceedings of the Symposium Informatica 78, Bled. S. Alagić et al.. Implementing CODASYL-type sets using B - trees, Vlth Congress of the Balkan Mathematicians, Varna, Bulgaria, 1977. S. Alagić et al.. Manipulating hierarchical databases, Journal Informatica, Ljubljana, Yugoslavia, 1978. S. Alagić, Developments in programming methodology, invited paper. Proceedings of the Symposium Informatica, Jahorina, Yugoslavia, 1978. S. Alagić et al.. Implementation of binary relational statements and operators in Pascal-R, Technical Report, Faculty of Electrical Engineering, Sarajevo. A. Kulenović and S. Alagić, Implementation of relational expressions and assignment statements in a Pascal/R system. Proceedings of the Symposium Informatica, Ljubljana, 1982. S. Alagić, Introducing relational systems in the assembly of products applications, Technical Publication, Research Community of Bosnia and Herzegovina, Sarajevo, 1984. S. Alagić, An approach to the design of information systems supported by database systems. Proceedings of the Symposium Informatica, Jahorina, Yugoslavia, 1986. S. Alagić, Spatial data modeling. Proceedings of the Symposium Informatica, Jahorina, Yugoslavia, 1986. S. Alagić, Conceptual versus relational modeling, invited paper. Proceedings of the Computer at the University Conference, Cavtat, Yugoslavia, 1986. S. Alagić, Object-oriented database programming in a relational environment extended with modules, Technical Report, Software Development Laboratory, Faculty of Electrical Engineering, University of Sarajevo, 1988. S. Alagić, Conceptual modeling: the arrow-theoretic perspective. Technical Report, Software Development Laboratory, Faculty of Electrical Engineering, University of Sarajevo, 1988. S. Alagić et al. Relational systems in production management systems. Journal of Technology, Science and Engineering, 32, Sarajevo, 1989. S. Alagić, MODULEX: A multiparadigm approach to database management. Technical Report, Software Development Laboratory, Faculty of Electrical Engineering, University of Sarajevo, 1989. S. Alagić, Integrating relational and object - oriented databases: A multiparadigm approach. Technical Report, 1989. S. Alagić and M. Alagić, Integrating data models by heterogeneous algebras. Technical Report, 1990. S. Alagić and N. Krdzalić, Generic low-level strongly-typed support for large scale persistent objects. Technical Report, Software Development Laboratory, Faculty of Electrical Engineering, University of Sarajevo, 1991. Other Books (in Serbo-Croatian) S. Alagić, Relational Databases, Svjetlost, Sarajevo, 1984. S. Alagić, Principles^of Programming, Svjetlost, Sarajevo, 1976. Edited by Anton P. Železnikar Using Fuzzy Modal Logic for Inferential Information Retrieval Jian-Yun Nie and Martin Brisebois Departement d'lnformatique et Recherche operationnelle Universite de Montreal C.P. 6128, succursale Centre-ville Montreal, Quebec H3C 3J7 Canada E-mail: {nie,brisebois}@iro.umontreal.ca Keywords: Information retrieval, fuzzy modal logic, uncertainty handhng Edited by: Xindong Wu Received: May 9, 1995 Revised: May 17, 1996 Accepted: June 7, 1996 Information Retrieval is becoming more and more important due to the information explosion. However, most existing systems only use simple keyword matching to identify relevant documents, resulting in unsatisfactory system performances. Recent approaches to IR dig into the inference process in order to solve this problem. Most of them are investigated within a probabilistic framework. The strict formalism of probability theory often confines our use of knowledge to only statistical knowledge (e.g. term connections based on their co-occurrences). Richer human-defined knowledge (e.g. manual thesauri) has not been incorporated successfully. In this paper, we consider the fuzzy modal logic framework in the definition of our inferential model. A document description is associated to a fuzzy world. Inference is based on the fuzzy accessibility relations between worlds. Due to the flexibility of the fuzzy logic framework, human-defined knowledge may be incorporated into our system. We report our experiments on a test corpus using a general manual thesaurus. It is shown that human-defined knowledge, when adapted to the application area and used adequately, leads to great improvements in system's performances. 1 Introduction In recent work, there is common agreement that more adequate relevance estimation should be baThe goal of an Information Retrieval (IR) system sed on inference rather than direct keyword mat-is to select the documents relevant to a given in- ching [9, 25, 43, 41]. That is, the relevance rela-formation need out of a document database. The tionship between a document and a query should present information explosion increases the im- be inferred using available knowledge. This infe-portance of this area. We are often faced with the rence, however, cannot be performed with corn-problem of finding out relevant information from plete certainty as in classical logic due to the una huge information mass. Traditional approaches certainty inherent in the concept of relevance: one to IR use direct keyword matching between docu- often cannot determine with complete certainty ment and query representations in order to select whether a document is relevant or not. In IR, relevant documents. The most critical point goes uncertainty is always associated to the inference as follows: if a document is described by a key- process, word different from those given in a query, then the document cannot be selected although it may In order to deal with this uncertainty, proba-be highly related. This situation often occurs in bility theory has been a commonly used tool in real cases as documents are written and sought IR [1, 14, 26, 42, 34]. Probabilistic models usu-by different persons. älly attempt to determine the relationship be- tween a document and a query through a set of terms which are considered as features. Differences between probabilistic models often lie into the connections considered among the terms [14]. Within any of these models, simplifying independence assumptions have always been made about these connections and some of them are inconsistent [8]. Although simplifications facihtate the implementation, they do not correspond to the user's inference process. For example, within the Binary-independent model, terms are assumed to be completely independent. In reality, they are not. In order to bring the inference process closer to the user's one, more flexible inference such as that in logic should be used in an IR model. Indeed, inference is above all a logical operation. The logical component seems to be diluted in previous models which place much emphasis on the treatment of uncertainty. The framework required for inference in IR would combine a logic with an appropriate handling of uncertainty [34]. The definition of such a framework is the first goal of our study. Within the strict probabilistic framework, inferential approaches are often confined to using only statistical relations among terms. Two different methods have been used to extract such knowledge automatically: — by considering term co-occurrences in the document collection [33]. In this case, two terms which often co-occur are considered strongly related. — by considering user relevance feedback [16, 21]. If two documents are judged relevant simultaneously by a user, then it is considered that there is some relation between the terms of the two documents. Both methods suffer from poor recovery of the application area. This problem stands out particularly in the second approach based solely on relevance feedback because availability of relevance feedback information is often limited in practice. Relevance feedback only allows to revise a small part of relations among terms. In the first approach, relations obtained from statistics may be very different from the genuine relations: truly connected terms may be overlooked [38] whereas truly independent terms may be put in relation [31]. There is still a third group of term relations used in IR: those established by human experts in some application areas. These relations are often stored in a thesaurus. Due to the lack of strict quantitative measurement of such relations, it is difficult to use them in probabilistic models. However, with the recent development of large thesauri (for example, Wordnet [27]), these relations have quite a good coverage of application areas. A manual thesaurus is then a valuable source of knowledge for IR. Thus another goal of this study is to provide a flexible model in which human-defined knowledge can easily be incorporated. This paper is organized as follows. We briefly review previous work on inferential IR and thesaurus-based approaches in Section 2. Section 3 describes our inferential approach within a fuzzy modal logic framework. This approach is derived from a general idea suggested by van Rijs-bergen in [43]. Two alternative approaches are proposed to replace the initial idea of van Rijs-bergen, and thus make it more feasible. We then describe, in Section 4, our method of adapting a manual thesaurus for our fuzzy inferential approach. Section 5 comments some experimental results. Finally, concluding remarks are given in Section 6. 2 Previous work on inferential and thesaurus-based IR A lot of research has been conducted in both inferential and thesaurus-based retrieval. Although they are closely related, they represent two different aspects: the former emphasizes methodology of the document-query comparison while the latter tries to implement a given approach using a thesaurus. 2.1 Inferential retrieval Inferential approaches have usually been defined in a probabilistic perspective. One of the earliest attempts is to add a term dependence tree in a probabilistic model [42]. This endows the model with more inferential power in comparison with the previous Binary-independent model. A document is considered to be relevant (to some extent) if the requirements of a given query may be inferred from the document through the term dependence tree. However, the inferential power in this model is limited. More recently, Bayesian networks [30] have been used in IR with great success [41], This method is based on a pre-established inferential structure, divided into several layers (document, concept, term, query and information need). Elements in one layer may be connected (with a certain probability) to the elements of adjacent layers, but no connection is allowed among elements from the same layer. Two operations are important in this approach: the inference of the relationship between the documents and a given information need, and the revision of the connections established in the structure according to user relevance feedback. The former is a forward pro-babihty propagation and the latter a backward probabihty revision. Although Bayesian networks are able to incorporate quite complex relations, the assumption of independence among elements of the same layer is still too strong. For instance, for the term layer, the independence assumption implies that, for the model to correspond completely to the reality, one has to determine a set of elementary terms that are independent of each other. In practice, this assumption is difficult to be satisfied. There are also attempts to develop a suitable logic for information retrieval coping with inference. The idea proposed by van Rijsbergen [43, 44] has attracted wide attention. It suggests that relevance is indeed a non-classical logical impHcation: given a document and a query represented by logical sentences d and q, the relevance of the document to the query may be expressed as the implication d q which is different from the material impHcation d D q. As d ^ q is uncertain in general, a function P{d —> q) should be defined to measure the degree of certainty of d —> q. Van Rijsbergen proposes the following uncertainty principle guiding the definition of P: Given any two sentences x and y, a measure of the uncertainty of y x relative to a given data set, is determined by the minimal extent to which we have to add information to the data set, to establish the truth of j/ —> x. It has been shown [29] that, by giving an adequate definition of the evaluation oiP{d —> q), most existing IR models may be generated from the above idea. Nevertheless, the adequate general definition of P{d q) is still an issue. Wong and Yao [48] try to implement this idea in a more concrete model. They abandon the possible-world semantics suggested by van Rijsbergen, and propose a probabilistic inference instead. However, the logical component becomes diluted as in other probabifistic approaches and the flexibility in inference is much restricted. Our present work is based on the same general idea, but we will stay within a logical framework for higher inference fiexibihty. 2.2 Constructing and using thesauri Thesauri used in IR may be divided into two categories according to their construction: automatically or manually constructed. The former are usually based on statistics on word (co-)occurrences. While this kind of thesaurus may help users to some extent, their utilization in early systems shows that their impact on the global effectiveness is limited [39]. The reason for this is twofold. First, real relations (e.g. synonymy) can hardly be identified statistically. In fact, words very similar in meaning tend to repulse from each other in continuous portions of text [38]. For example, "document retrieval", "text retrieval" and "information retrieval" are rarely used simultaneously. Second, as users are likely to formulate their queries using common words, a statistical thesaurus will expand these queries with other highly frequent terms. These latter have a low discrimination power of relevant documents, similar to the original terms. Expanding a query by adding those terms with the highest co-occurrence frequency may not bring much more new information to it [31]. Even though one restrains the consideration of term co-occurrences within some syntactic contexts (e.g. noun phrases) [15, 18, 19], system performance only benefits marginally [15]. Recent work pays more and more attention to manually constructed thesauri. Initial experiments have been conducted using the vector space model [11, 12]. Related terms were simply added to the query vector according to a weighting factor. By the end of the 1980s, interest increased in manually constructed thesauri. They began were seen as semantic networks in which it was possible to use the spreading activation technique to measure similarity between queries and documents [7, 35]. Initiated by Rada [32], a great deal of efforts have been spent in defining a IR suited metric over semantic networks [5, 20, 23, 24]. All these models measure the similarity between two terms mainly according to the topography of the thesaurus (the number and length of hnks). Moreover, they often consider only "is-a" relations. Two problems may occur in these systems. First, the estimation of the strength of term connections which is based heavily (if not only) on the use of thesaurus topography may fail to reflect the real strength of the connections. This strength also depends on the nature of the relations between them which affects their relevance to some appHcation area. Second, the metrics used to measure term connection are often symmetric; for a metric m, we have m(a, b) = m{b, a) for any pair of terms a and b. This property is obviously counterintuitive. For example, a document about object-oriented languages should be more relevant to a query on programming languages than in the reverse situation. Thesaurus-based query evaluation gained in popularity because large general thesauri became available. The use of such a thesaurus in IR has been recently studied by Voorhees [45, 46]. She used the thesaurus Wordnet [27] for query expansion in an IR system based on a vector space model. However, her attempts yield a negative conclusion: when a query is expanded using Wordnet, retrieval performances suffer. In our opinion, these results are due to her particular use of the thesaurus. 1. As Wordnet is a general thesaurus, a relation may lead to either a relevant term or an irrelevant one with respect to the application area. It is then necessary to determine and measure the relevance of the related term before using it in query expansion. A coarse measurement may lead to a complete failure. 2. The vector space model seems inappropriate for this kind of query expansion. In fact, when a related term is added to a query vector, the corresponding sense is artificially enhanced because it is represented several times in the new vector. The enhanced senses are not the ones which are judged important by the user, but those which are involved in many thesaurus relations. 3 Modeling the inferential approach in a fuzzy modal logic framework Since the late 1980s, several new approaches have been developed in order to base query evaluation on inference [6, 9, 25, 43, 44, 41). However, only a few theoretical frameworks suggested allow the unification of different approaches in a single formalism. The idea suggested by van Rijsber-gen [43, 44] is one of them. In order to develop a general approach, we adopt the idea of van Rijsbergen. This section will show how the idea may be modified in order to facilitate its implementation. Then the suggested approach will be modeled using fuzzy modal logic. Finally, some implementation aspects will be considered. 3.1 Rationale Let us first re-express the uncertainty principle of van Rijsbergen as a formula. We identify a document description d as ?/ in the uncertainty principle, a query expression q as x, and the knowledge of the system K as the data set. By knowledge, we mean a set of (weighted) term relations. Applying the uncertainty principle to IR means that relevance should be estimated as the degree of certainty of the following expression: K l=d^ g Let us denote the degree of certainty of this formula by the function Paid q). Suppose there is a function Ext{K, K') which measures the amount of extension from K to K', and a function F which determines the corresponding degree of certainty for an extension amount. Then according to van Rijsbergen, the uncertainty oi K \= d ^ q should be determined by the minimal Ext{K,K') such that K' 4 —>■ q becomes true i.e.: PKid = F(inf[Ext(K, K') : K'dq]) or Pfi{d -^q) = sup[F{Ext(K,K') : K'dg)] Although most existing IR models may be re-expressed in terms of the uncertainty principle by a proper definition of the functions Ext and F [29], the above formulation is difficult to implement in practice due to the following two facts. First, changes must be made on the system's knowledge K and these changes must be measured in terms of degree of certainty. To do this requires the definition of meta-knowledge handling such changes, which is an extremely difficult task. Second, this formulation still requires the complete satisfaction oi K' \= d ^ q. In practice, this criterion is almost never met. In order to transform this general idea into an inferential approach which is easier to implement, we suggest the following two alternative approaches based on modifications of d and q respectively: Approach 1 In order to estimate the degree of certainty oi K \= d ^ q, we must identify all the document descriptions d' related to d. The degree of certainty oi K \= d ^ q is determined by both the degree of relatedness of d' to d and the degree of certainty oi K d' q for all the d's. Approach 2 In order to estimate the degree of certainty of K (= d —> g, we must identify all the query expressions q' related to q. The degree of certainty oi K d q is determined by both the degree of relatedness of q' to q and the degree of certainty of K |= d —> q' for all the q's. As these approaches are based on modifications of the document or the query descriptions respectively, we call them document-driven and query-driven approaches. The two approaches are very similar. So we will base our explanation on the document-driven approach. In fact, the document-driven approach can also be derived from the following classical inference: ÌAdB)A{BDC)\=ADC Putting the uncertainty aspect aside, we can expect the following corresponding inference in IR: {d ^d')A{d'^q)\=d-^q If there are several such d', then we have: That is, whenever we have a such that d —y d^ and d'^ q, then we can conclude d q. Considering the uncertainty involved, the degree of certainty of the left side in the above inference is a good estimate of that of the right side. That is P{d -^q) = P In this study, we consider P as a fuzzy function. In fuzzy contexts, following [10], conjunctions and disjunctions should be evaluated by a triangular norm A and its co-norm V respectively. A triangular norm A is a function from [0,1] x [0,1] to [0,1] that satisfies the following conditions (where € [0,1]): • 1. A{x,y) = A{y,x)] 2. A(x,A(7j,2)) = A((A(x,y),z); 3. Ifa; < x' and y < y', then A{x,y) < A{x', y') The min function and multiplication of real numbers are two examples of triangular norm. A co-norm V is defined as: V(x,2/) = 1-A[(1-X),(1-2/)]. The max function is the co-norm of min, and x -)-y — xy is the co-norm of multiplication of real numbers. Using a triangular norm A and its co-norm V in our case, the degree of certainty of P{d —» q) may be then evaluated as follows: P{d^q) = i = (1) i The two implications found in the right side of formula (1) may be interpreted in the following way: - P(d —» d') measures the degree of relatedness of a new document description d' to d. - P{d' —^ q) measures the satisfiability of the query q by the new document description d'. Note. that up to now, we have assumed that both the document description d and the query expression g are classicàl-logic expressions. In fact, although queries are often expressed as Boolean expressions of terms, documents are usually-described as a set of weighted terms as follows: where pi is a term and (Xi its weight in the document. If we consider a term as corresponding to a proposition, a query expression corresponds to a Boolean logical expression, but a document description does not. In this context, it is difficult to evaluate directly P{d d!) for two sets of weighted propositions. One alternative is to define a fuzzy degree of relatedness between the sets d and d' to replace P{d —>■ d'). Yet another solution is to consider a document description as corresponding to a fuzzy world in fuzzy modal logic [37, 49]. The relatedness between two document descriptions can then be modeled as the degree of accessibility between their corresponding worlds. This is the approach we take. 3.2 A logical model for inferential IR Fuzzy modal logic has been first proposed by Schotch [37] and later elaborated by Ying [49]. The main idea underlying this logic is to fuzzify both the characteristic function of a world and the accessibility relation between worlds. Let IP be a a set of atomic propositions, F be the language of the classical modal logic [4], and W be a non-empty set of worlds in the (modified) possible-world semantics. 1. Each world if e W is assigned a characteristic function C : W [0, if such that Cp{w) gives the fuzzy truth value of atomic proposition p in world w. 2. The function ^ : (W x W) ^ [0,1] is defined in order to measure the fuzzy degree of accessibility from one world to another. This function is reflexive, i.e. 6{w, w) — 1 for any w€W. A model of the fuzzy modal logic, which is slightly generalized from that in [49], is defined by the triple (W,6,V), where y : F [0,assigns a truth valuation function Vw{*) to each world w e W. The function Vw gives each formula a fuzzy value as follows: - VM = Cp{w), p € P; - VUAAB) = A[VUA),V^{B)y, luew Note that the evaluation for operators V and □ may be obtained using the following definitions: Ay B =def -'hA A -.5) DA =def -O-A To compare the above evaluation with V^(Oj4) and P{d —> q) in formula (1), we can observe the following analogy between d and w, between d' and w', between P{d —> d') and S{w,w'), and between P(d' q) and V-^'iA). This analogy strongly suggests that V.wj^{Oq) may suitably models P{d —> q) if we could determine a world Wd giving the same evaluation of propositions as d. The identification of such a world will be described in Section 3.3. For the moment, let us assume such a world and see how the model can be applied to IR. Note that the evaluation modeled by allows only one step of inference, i.e. only the document description directly related to the initial one is considered. This restriction prevents from establishing a connection between a document described by "database" and a query on "natural science" because (at least) two inference steps are required: from "database" to "computer science" and from "computer science" to "natural science". In order to allow longer inference, document relevance should be modeled as V^Aooq) V^,{OOOq) which correspond respectively to inference lengths 2, 3, ..., and n. A longer inference process implies the examination of more potential document-query matchings, thus allows the system to consider the documents that are more loosely related to the query. So a longer inference process means a wider range of document examination, thus a higher inferential power. This, however, is beneficial only when the knowledge (term connections) used in the inference is sound. Figure 1: A general inference structure. (In this figure, reflexive derivations are not shown. An arrow indicates a derivation, and a dotted arrow indicates a direct evaluation of the query.) Otherwise, such an inference would lead to the retrieval of many irrelevant documents. This will be shown in our experiments. The inference process over all the documents in the collection may be seen in a way similar to that of the Bayesian network model [41] (Figure 1). There are three different layers in our system: at the top level, there are initial document descriptions, each corresponding to a world in fuzzy possible-world semantics. The bottom layer is the query layer. Between them lies the inference layer from which new worlds are derived and connected to the initial ones. Any initial document description from which a connection may be established with the query through the inference layer is a potentially relevant document. There is an important difference between the Bayesian network approach and ours. In the Bayesian network approach, the inference layer is further divided into two sub layers: term layer and concept layer. Each of them contains elements (terms or concepts) that are assumed to be independent. Connections can only be established from terms to concepts. We can make the following two remarks on this approach. 1. The independence assumption for elements from the same layer is not reahstic: Documents cannot be represented by a set of inde- pendent terms or concepts. Terms, as well as concepts, are inter-dependent in most application areas. 2. Inference from a document to a query in this approach is limited to three steps: from documents to terms, from terms to concepts, and from concepts to queries. In our approach, we do not make the independence assumption on the elements within the inference layer, nor do we limit inference length to 3. Within the inference layer, worlds can freely connect to each other, provided that the connection is allowed by the system's knowledge and it is within the inference length under consideration. We can also compare our approach with previous IR models based on fuzzy set theory [3, 22, 33, 47], These latter are often based on a direct fuzzy matching between documents and queries. They can be easily described in our model by withdrawing the inference process, i.e. they indeed correspond to In some cases, a fuzzy thesaurus is also incorporated, but only used for matching a document term directly with a query term. This is equivalent to adding an inference layer between documents and queries which contains independent nodes. It can still be considered as a limited case of our model (i.e. The goal of using fuzzy modal logic is to provide a suitable framework to describe the inferential approach. We do not intend to develop the logic from a formal point of view. For this, one can refer to [37, 49]. We are concerned with the question of how the inferential approach modeled here can be implemented in practice (in particular, by incorporating human-defined thesaurus as the system's knowledge). To accomplish such an implementation, two problems must be solved: 1. the determination of the world Wd which corresponds to a document description d\ 2. the determination of the related worlds and the fuzzy relation d between the worlds. We will deal with these problems in the following section. 3.3 Applying the model to IR We will use a derivational approach to define W from the model: a subset of W corresponding to the initial document descriptions is first defined, and other worlds are derived from them. The world Wd In IR, a document is usually described by a set of weighted terms. This result is obtained through an indexing process. In previous fuzzy logic approaches [3, 2, 22, 28, 47], each term is considered to be atomic proposition. In addition, a term which does not occur in a document description is assumed to have a weight of 0 in this document. We make the same hypothesis here. For example, suppose a document is described as follows: where pi is a proposition (or term) and a, its weight in the document. Then the propositions P2, ■ ■■, Pn have the truth values «i, a2, .. •, «n respectively, and other propositions absent from this document is assumed to have fuzzy truth value 0. It follows that the truth value of every atomic proposition is determined within a document description. This means that a document description uniquely determines a fuzzy world Wd which is associated with a characteristic function such that: Cp{wd) = _ j ap if p is weighted ctp in d; 0 if p is absent in d Given a set of document descriptions, each pertaining to a document in the collection, we can then establish a set of worlds in fuzzy modal logic. We will call these worlds the initial worlds. Prom the initial worlds, we can derive other worlds by applying domain knowledge. We will see how the derivation may be made. The function Ó The principle of the derivation goes as follows: Prom a world w in which a proposition A is asserted to some extent, if another proposition B is related to A to some extent, then the proposition B may be inferred with a degree of certainty, and the addition of the inferred proposition leads to a possible world w'. This process is very similar to reasoning under uncertainty in fuzzy logic in which uncertain inference is made possible due to the generalized Modus Ponens [10, 50]. An inference rule that we can derive from the generalized Modus Ponens is the following {a,ß G [0,1]): aA, ADß B where aA means "A is true to extent a", and ADß B means "A D B is true to extent ß". The rule may be read: from the uncertain fact aA and the uncertain implication (or knowledge) ADß B follows the conclusion A{a, ß)B(i.e. B may be asserted to extent A{a,ß)). Note that this inference is done in complete certainty although both the fact and the knowledge used as well as the conclusion are uncertain. The problem with this inference rule is that it does not tolerate the use of inconsistent pieces of knowledge. For example, from aA and A Dp B, we may conclude A{a,ß)B-, while at the same time, from a A and A Dß> ->B, we can also conclude A{a, ß')-^B which may contradict A{a,ß)B. This inconsistency occurs within human-defined knowledge [40] which may contain both ADß B and A{a,ß')-'B. In order to allow the use of weighted or loosely defined knowledge in our inference, we make use of the following fuzzy inference rule instead: In addition, we have implicitly 6{wi,wi) = 1, for any i. aA,ADß B aB ß where both a. and ß are within [0,1]. This rule says that given the uncertain fact aA and the uncertain imphcation relation A Dß B, we can infer the uncertain conclusion aB, but the inference itself is certain only to extent ß. In this rule, we distinguish the role of a piece of knowledge from that of a fact: an uncertainty on the former affects the validity of the entire inference process while an uncertainty on the latter only affects the certainty of the conclusion. Applying the new inference rule to our model, we can obtain the following derivation of new worlds and the definition of the function 6. Given a world w in which a proposition p has the truth value dp and a piece of knowledge (p Dß p'), adding the conclusion app' leads to another world w' in which the truth value of proposition p' is modified to ap, and the accessibility of w' from w is: 6(w,w') = ß Here we only consider prepositional modal systems. Thus, from a given world, there must be a finite number of derivations, since we have finitely many propositions. The set W of worlds is finite. We can see therefore that the whole approach is based on a set of knowledge represented as fuzzy logical implications (e.g. p Dß p'). The definition of a knowledge set is a crucial problem. We will discuss this problem in detail in Section 4. For the moment, we assume that such a knowledge set is available. Let us now illustrate world derivation and query evaluation by an example. Suppose that we have five atomic propositions a, 6, c, d, and e, and that the initial world wq is as shown in Figure 2. Suppose further that we have the following uncertain implication relations in our system: (a Dß,, c), (Ò Dß,^ d) and (c Dß,, e). We can derive the worlds and W2 by applying the inference rules using the first two relations. From these worlds, more new worlds are derived, as shown in the figure. The accessibility between the worlds is also illustrated in the figure. For example: 6{wo,Wi) = 6(w2,W3) = ßac Figure 2: An example of derivation of new worlds. (The accessibility from a world to itself is not shown in this figure.) Given a sentence qi = (ò A c), the truth value of qi in the possible worlds accessible from wo is as follows: V^M = K;,(gi)=0 = A(K.,(6),K,,(c)) = A(a„,a(,) So we have the following evaluation of Oqi in the world wq: - V[0> 0] = ^{ßac,o:a,ab) Now using the same calculation, if we have another sentence q2 = {b /\ e), the evaluation of Vwoi'^li) will be 0, because in any world directly accessible from uiq, e is valued to 0. However, has a non-zero value due to UI4: V^,{OOq2) = Aißac,A[ß,e,A{aa,ab)]) - A{ßac,ßce,aa,Olb) This second example shows that with a longer inference, more "distant" but "related" documents may be retrieved. Note that both the distance and the relatedness are dependent on the knowledge incorporated in the system. If the incorporated knowledge consists off all and only genuine knowledge in the application area, they are conceptual distance and relatedness. In practice, this is not the case. Nevertheless, we can still expect that the distance and the relatedness are coherent with their conceptual counterparts. Document-driven vs. query-driven It is easy to understand the document-driven approach in the modal logic model. A document description corresponds to a world. Any change in the document description using uncertain knowledge defined in the system derives to another document description. Given a query expression q, its evaluation relative to a document described by d is determined by the evaluation of q in all the descriptions accessible from (related to) d, on one hand, and the degree of accessibility of these descriptions from d, on the other. It is more difficult to describe the query-driven approach in the modal logic model. Instead, query-driven approach may be seen as follows. The query language is extended by allowing weighted propositions. A weighted expression p^ is intended to capture the uncertain relevance between a proposition and another related one. A weighted proposition p^ is evaluated as follows: VUp^) = Aiß,VM). We make use of this expression in query modification in the following way. Consider a query expressed as a logical sentence q in which proposition p appears. If the system contains the implication relation (pi Dß p), i.e. p is implied by Pi to the extent ß, then the proposition p in q can be expanded to (p Vpf). This latter expression indicates that to satisfy the proposition p, we can either satisfy p directly, or we can satisfy pi instead. However, in the second case, the satisfaction of the initial proposition p is moderated by the extent ß to which the two propositions are related. The expansion process is to be applied to any proposition in a query. Longer expansion implies also expansion with respect to the added propositions. For example, if the added proposition Pi is to be expanded using the relation p2 Dß^ pi, then the expanded form is: j^i'' V ■ Following such expansions, the query expression q' obtained is to be evaluated relative to an initial document description d (or in the corresponding world Wd) in order to estimate the relevance of the document. The above query-driven approach is equivalent to the document-driven approach when the inference length is sufficiently high. Indeed, when there is a new proposition added to the query, it is equivalent to take into account a new possible world in a document-driven approach. If the inference length is high enough, then all the possible worlds related to the initial world will be taken into account in the document-driven approach. Equivalently, all the propositions related to those included in the initial query are added to the query in the query-driven approach. In this case, the two approaches result in the same evaluation. However, when the inference length is limited, there may be differences between the two approaches because an inference length does not restrain to the same scope of consideration in the two approaches. For instance, in the example shown in Figure 2, if inference length is limited to 1, the document-driven approach will consider wq, wi and W2 in its evaluation of a query. In the query-driven approach, however, wz will also be taken into account. If inference length is limited to 2, then the document-driven approach will consider Wo, wi, W2, W3 and W4, while the query-driven approach will consider loi, W2, W3, W4 and W5. Nevertheless, if we assume that Figure 2 shows a complete possible worlds structure (with all the possible worlds), then the two approaches will result in the same evaluation when the inference length is higher than 2 (i.e. all the possible worlds are considered). Let us give more examples for the query-driven approach. Suppose we are in the same situation as in the example shown in Figure 2. Given a query expressed as gi = (b A c), the query may be modified by expanding the proposition c to (cVa^'"^), using the implication (a Dß^^ c). There is no expansion possible on b. Then the new query q[ is as follows: q[ = (òA(cVa^"=)) Evaluating this new query with respect to the initial document description (or the corresponding world wq) yields the following result: = A{ab,A{ßac,aa)) = A{aa,ab,ßac)- This is the same evaluation as that obtained by a document-driven approach. In the same way, the query q2 = {b A e) may be expanded to: ^^ = (6A(eVc^«)) (length 1) q'-i = (Ò A (e V c/'- V (length 2) We can obtain: VM) = 0, = A(ab,V{0,0,A{A{ßac,ßce),aa))) = A{aa,ab,ßac,ßce) These results are also the same as those obtained in the document-driven approach. However, if qs = (c A d) and the inference length is limited to 1, then using the document-driven approach results in Vyjg{Oq3) = 0; whereby using the query-driven approach gives q's = ((c V a^-) A (d V ò^^'')) and = A{A{aa, ßac), A{ab, ßbd)) + 0. So the two approaches lead to different query evaluations. It should be noted that the difference between the two approaches is due to the limitation of the consideration scope, i.e. one step of inference in the document-driven approach modifies the characteristic function over only one proposition at a time. However, one step of inference in the query-driven approach may expand any number of atomic propositions found in the query. In the unlimited case (with a high inference length), the modal logic model provides a suitable explanation to the query-driven approach, which is exactly the approach called query expansion. Hence, our model also provides a theoretical framework for this latter operation which, until now, has always been described in an aà hoc way. 4 Inference using a manual thesaurus Although human-defined term relationships are more rehable (in terms of precision and domain coverage) than automatically extracted ones, they do not tell to what degree a document represented by one term is relevant to a query represented by another term. For example, a relationship of meronymy (HAS) between computer and processor does not determine precisely relevance of a document about computer for a query about processor. In our discussion we will refer to this relevance as term relevance (in contrast to document relevance). One term is relevant to another if a document represented by the first term is relevant to the query represented by the second term alone. Indeed, term relevance represents the simplest case of document relevance. In order to estimate more complex cases of document relevance, we first have to make an estimation of the strength of term relevance. Term relevance is uncertain as document relevance. We represent an uncertain term relevance with a fuzzy implication relation such as a Dp b, where ß € [0,1]. In this way, the entire thesaurus may be represented as a set of fuzzy term relevance relations: {(a Dß b),...}. The key problem in using a manual thesaurus in our inferential approach hes in the estimation of term relevance strength ß given a thesaurus relation between two terms. Learning term relevance relations from the user The decision about how relevant one term is to another is closely bound to the application area, the user's opinion and his/her requirements. We cannot expect the system to give a fixed and unique estimation of term relevance that is suited to every situation. Rather, several estimations may be made from a thesaurus, each corresponding to a particular view of a user or a group of users. In order to transform a manual thesaurus to a set of fuzzy relations which are adapted to the user's requirements, we make use of user relevance feedback. The principle goes as follows. The system gives a tentative query evaluation and provides an answer (a set of ordered documents). Then the user is required to give his or her own relevance evaluation of the retrieved documents The user's evaluation is used by the system to revise the strength of term relevance relation in order to better fit the user's evaluation. More specifically, for a given thesaurus relation between a and 6, the strength ß of the corresponding relevance relation is determined as follows: 1. If a user's query contains a, the system carries out a tentative evaluation with an initial fuzzy value ß for the thesaurus relation, i.e. the query is expanded with b^. 2. The user examines (possibly part of) the list of retrieved documents and indicates whether they are relevant or not. 3. Then the value ß is modified to both ß' = min[l,/3-(l-t-e)] ß" = ß-a-e). where e G [0,1] is the change scale. The query is evaluated again with ß' and ß". 4. The fuzzy value for this relation is adjusted to the value which leads to the best answer (best partial average precision, see explanation below), i.e. it either remains as ß or it is changed to ß' or ß". The quality of an answer in IR is usually measured by the average precision [36]. For this, we need to know the total number of relevant documents in the corpus, and this is often impossible in real applications. So we use a modified measure, partial average precision, which measures the average precision with respect to only the documents found in the system's answer. The approach used to adjust the strength of a relevance relation is simple. However, each adjustment requires three query evaluations (with three tentative strengths). So it is time-consuming. However, the purpose of our experiments is to see whether a manual thesaurus can be incorporated as a knowledge base rather than to achieve efficiency. Nevertheless, the simple adjustment process needs to be improved in efficiency should it be used in a real system. Learning for a group of thesaurus relations vs. for individual relations Due to the great number of relations in a thesaurus, if we apply the above learning process to each individual thesaurus relation, the learning process would be very long. This is because for every user relevance judgment, only a small number of relations are concerned. Adjusting all the relations requires a great deal of relevance feedback information. In order to accelerate the learning process, a good compromise is to suppose that relations of the same type correspond to approximately the same relevance strength. For example, given the following two relations of the same type hypernymy: computer ^hypernymy machine maple ^hypernymy tree we assume that the relevance strength of "machine" to "computer" is similar to that of "tree" to "maple". Under this assumption, the above process is applied to different types of relations, thus quickly covers every thesaurus relation. However, accuracy may be compromised. Thus, once sufficiently accurate strengths have been obtained from learning for different types of relations, learning for individual relations follows. Our learning process may thus be divided into a quick learning step and a finer adjustment step. 5 Experiments The manual thesaurus approach in Section 4 has been tested on the CACM corpus [13] which comprises 3204 documents published in the Communications of the ACM. Answers to a set of 50 queries are provided by experts, and they are used to evaluate the system's answers. Note that the 50 queries are given both in natural language and in Boolean expression of terms. We used the Boolean queries in our experiments. Document descriptions are obtained using an automatic indexing process based on document's title and abstract and using tf*idf weighting method. Thesaurus and its utilization The thesaurus Wordnet [27] is used to establish term relevance relations. Wordnet contains a large set of human-defined relationships among over 54,000 English words and terms. Table 1 shows the types of relations it provides. In Wordnet, a word (or term) sense is represented by a group of terms that are synonyms under this sense. Such a group is called a synset. A given a word (or term) may be comprised in several synsets. The synonymy relation is implicit relation example synonymy computer data processor antonymy big small hyponymy (is-a) tree =>hyponymy maple hypernymy (a-kind-of) maple =^hypernymy tree meronymy (is-part-of) . computer =>hypernymy processor holonymy (has-a) processor =^hypernymy Computer Table 1: Some relations offered by Wordnet where the notation a h indicates that h is one of the word meanings for which the relation (b rei a) holds. within each synset. Other relations are established among synsets. Here we give an example to illustrate the organization of Wordnet. We denote a synset by {.. .}, and a given type of relation by =>type- The word computer is included in the following two synsets: Sense 1: {computer, data processor, electronic computer, information processing system} =>hypernymy {machine} Sense 2: {calculator, reckoner, figurer, estimator, computer} ~^hypernymy { ®xpert} That is, computer has two different meanings: one for a machine (sense 1) and another for an expert (sense 2). The synset after =>hypernymy is the hypernym synset of the given sense. The hyponymy relation related to computer is defined as follows: Sense 1: . computer =>iiyponymy {analog computer, analogue computer} {nvimber cruncher, number-cruncher} {digital computer} . {pari-mutuel machine, totalizer, totalizator} {tactical computer} Sense 2: computer =>hyponymy {number cruncher, number-cruncher} {statistician, actuary} The meronymy relation exists only for sense 1: computer =>meronymy {cathode-ray tube, CRT} {chip, microchip, micro chip, silicon chip} {computer accessory} {computer circuit} {busbar, bus-bar, bus} {analog-digital converter} {disk cache} {diskette, floppy, floppy disk} {hardware, computer hardware} {central processing unit, CPU, C.P.U., central, processor, mainframe} {keyboard} {monitor} In Section 3, we have defined both query-driven and document-driven approaches. With the query-drive approach, higher efficiency is expected because 1. a query contains much less terms than a document, thus less inference may be applied to a query than to a document; 2. inferences made in query expansion are global (i.e. applicable to all the documents) while inferences made in a document description are local. When the document-driven approach is used, inferences must be repeated for each document, which is very costly. Therefore, we implement the query-driven approach as follows. Each term in a Boolean query is used to find out all the synsets connected by each type of relation in Wordnet. Then the terms in a related synset are weighted with the relevance strength of the relation, and connected to the initial term with V. For example, if the initial query is q = 'computer', and if relevance strengths are set such that the terms within the first synset above are attributed with ßi and the terms within the second synset with ß2, then the expanded query q' with "synonymy" relation alone is as follows: q' = 'computer' V 'data processor 'electronic computer' V ßi v 'information processing system' V ' computer'''i V 'calculatory 'reckonery 'figurer'^' V 'estimatorV ßi ß2 'computer' This query is further expanded with other types of relations from the term 'computer'. Compound terms are represented as a conjunction of simple terms after expansion. For example, 'data processor' will be replaced by ('data' A 'processor'). This is necessary since all the documents have been indexed by simple words. The decomposition of compound terms is a source of retrieval noise. For example, when 'data processor' is broken up, a document about 'data' will also be considered as an answer to a query about 'computer'. We believe that a better approach is to allow indexing documents with compound terms and to keep the related compound terms found in the thesaurus unchanged. The expanded query is very heavy, especially when long inferences are apphed. However, many new terms are added with very low weight. Thus, by setting a threshold, the expanded query can be reduced to an acceptable size. Furthermore many added terms do not correspond to any document so they do not contribute to query evaluation. Learning for different types of relations The 50 evaluated queries are randomly distributed among 5 groups of lO's queries. Each group is used in turn as the test set of queries while the others are used as training data for the adjustment of term relevance strength. In so doing, we assumed that the 50 queries were evaluated by experts having the same background and judgment criteria. This assumption was made due to the lack of adequate training and test data. We also assume that relations of the same type share the same relevance strength. At the beginning of each training process, the relevance strength of each type of relation was arbitrarily set to 1. Various values for the change scale e have been tested. It was observed that with a too low value of e, relevance strengths change too slowly while with a too high value of e, relevance strengths become unstable. In our case, the value 0.15 offers a good compromise between learning speed and stabilization. Figure 3 shows the average evolution (over the 5 training processes) of relevance strength for each type of relation as learning proceeds. Note that this figure is strongly thesaurus- and corpus-dependent. For example, the high relevance strength attributed to meronymy relation may be justified by the fact that only a few among the strongest of such relations are defined in Wordnet. Thus terms connected by those relations are usually highly relevant. Comparison of the system's performance We tested the approach with two different triangular norms: min and multiphcation of real numbers. We observed that the second gives much better results than the first in all cases. The reason is that min only considers the worst inference step to determine the degree of certainty for an inference path. This is a very partial consideration. On the other hand, by using multiplication of real numbers, every inference step contributes to the whole inference path. So inference is considered from a more detailed scale. In the following, we only report the results for the multiphcation of real numbers as our triangular norm. The fuzzy logic approach which does not have an inference process is used as the baseline model to compare against our approach. The query evaluation in the baseline model is defined as follows: vM V^i-^A) Cp{w), peP-, 1 - The system's performance is measured in terms of average ■precision [36] over 11 recall points (0%, 10%, ..., 100%). Table 2 gives a comparison between the system's performance using the baseline approach (Boolean query evaluation), our inferential approach before learning (i.e. with relevance strength for any relation set to 1) and after learning. In the inferential approach, the inference Syno ' Hypo---Hyper Mero Holo 1.000 Number of queries Figure 3: Evolution of relevance strength along with the learning process Approach test 1 test 2 test 3 test 4 test 5 Average precision Increase (%) Baseline 24.15 21.45 22.10 21.28 10.68 19.93 • Initial strength L = 1 L = 2 L = 3 24.75 23.90 17.97 13.64 9.00 20.83 18.54 10.80 11.40 6.67 15.01 6.87 4.67 4.20 4.81 17.85 13.64 7.11 -10.43 -31.56 -64.32 After learning L = 1 L = 2 L = 3 29.78 30.48 24.96 25.13 12.26 29.70 29.96 27.04 26.56 16.99 33.50 31.36 28.59 27.09 16.38 24.52 26.05 27.38 23.03 30.07 37.38 Table 2: Comparison of the system performances process has been applied with lengths 1, 2 and 3 respectively. The differences among the five tests (from test 1 to 5) are only related to our random distribution of queries among of test groups. They are caused by the different criteria used by human evaluators for the 50 queries. Our experiments do not address this aspect. What is much more significant is the difference between using the initial strengths or the strengths after learning and the evolution of system performances as inference length grows. The initial strength for all types of relations is set to 1. This may be considered as a coarse utilization of the thesaurus. In this case, the longer the inference is, the more the thesaurus is involved in the inference process, and the worse the system performance is. This observation may explain the negative impact of the same thesaurus over query evaluation found in some previous experiments [45, 46]. On the other hand, with a reasonable assignment of relevance strengths after learning, the use of the thesaurus improves the system's performance. Furthermore, the impro- vement increases with the inference length. This shows that after learning, the thesaurus is better adapted to the application area and its utilization becomes beneficial. Despite the noise brought by the thesaurus, the global effect is positive. As long as inference length increases, the time required for query evaluation also increases. When a query is expanded to length 1, the average evaluation time is about 5 seconds on a SPAR-Cstation 10. It becomes 10 seconds at length 2, and it is around 30 seconds at length 3. Figure 4 gives a closer look at the average system performances. It shows precision vs. recall for the baseline evaluation and for the evaluations with query expansion of various lengths. Learning for individual relations In order to compare between learning for types of relations and adapting for individual relations we used the same training data to adjust the relevance strengths of individual relations. In some cases, this individual adjustment succeeds in finding better relevance strength for relations. Here follow some examples. computer Do.27 data processor, electronic computer, information processing system ^0.0045 calculator, reckoner, figurer, estimator file Do.o94 data file I3o.oii3 single file, Indian file Do.oo82 file cabinet, fifing cabinet In these examples, relevant synsets in computer science are attributed with higher relevance strength than the irrelevant ones. In particular, in the case of computer, the strength for the first synset is sharply increased to 0.27 from around 0.05, while the other synset is decreased to 0.0045. These changes in strength are due to the uneven distribution of the words included in each synset among relevant and irrelevant documents. If the words of a synset appear more often in relevant documents than in irrelevant documents, then the strength for the synset (or for the synonymy relation) is increased. In the opposite case, it is decreased. However, this further adjustment does not succeed in every case. For the term "hardware", irrelevant synsets are attributed with higher strengths than the relevant one: hardware Do.i43 hardware "artifacts made of metal" D 0.041 hardware "military equipment" Do.oi29 hardware, computer hardware Note that the quoted parts are explanations, but not parts, of the synsets. That is, the individual adjustment succeeds in some cases, but fails in others. Globally, there are about the same number of successes as fails. So, the global system performance after individual adjustment remains almost unchanged. The average precision is slightly changed from 27.38 to 27.73 for inference paths of length 3. The minor difference may be explained by the lack of sufficient training data. It is possible that a greater difference would be produced if more training data were available. The minor difference may also depends on the way the thesaurus terms are incorporated in our expanded queries. In our experiments, compound thesaurus terms are broken into single words in order to match document indices which are single words. In so doing, a relevant compound term may be replaced by a set of ambiguous words. For example, the compound term "hash table" is unambiguously relevant to computer science, but its component words "hash" and "table" are less relevant: "table" may also be a furniture. Thus, from the component words, the system may erroneously conclude that "hash table" is not very relevant to computer science. We see then that the way in which we used the thesaurus in our query expansion is also a possible factor that harms the individual adjustment. 6 Concluding remarks In this paper, we have first defined an inferential approach to IR within a fuzzy modal logic framework. There are several reasons to replace the strict probabilistic framework by fuzzy modal logic. First, we want to enhance the logical component of our approach and to allow an unrestricted inference structure. Second, when human- Recall Figure 4: Detail of the comparison of the system performance defined knowledge is used in the inference process, we cannot expect that the knowledge may be always mapped to strict probabilistic dependencies among terms [40], Consequently, using human-defined knowledge in a strict probabilistic model may lead to inconsistencies. Fuzzy modal logic is then chosen as an appropriate alternative. As there is no quantitative measurement of the strength of term connections in a manual thesaurus, a thesaurus should be first transformed into a set of fuzzy relations among terms. We have made use of user relevance feedback in this transformation. This choice is consistent with the findings in [17] that user interaction is one of the main factors affecting the effectiveness of the use of a thesaurus. Our approach is different from previous inferential approaches due to the use of a more flexible framework which allows a free inference structure. This approach is also different from previous uses of manual thesauri in IR in which the strength of a connection between two terms was often determined according to the topology of the thesaurus (such as the number and length of links between terms). Our approach interacts with users through relevance feedback. Relevance feedback has been used in other IR approaches to expand the user's queries, to revise document representation, or to establish and revise relations among index terms. Although our goal is the same as this last use, there is an important difference: In establishing relations among terms, relevance feedback information has often been used alone in other approaches; in our approach, term relations established are within the scope of relations stored in a thesaurus, thus much less noise is expected. Our experiments showed a significant increase in system performances when a manual thesaurus is incorporated in this way. Although our experimental results strongly support the hypothesis that a thesaurus-based inference procedure is suitable to the IR reality, several points should be improved in our implementation. First, many Wordnet relations lead to terms that do not correspond to any document. During the first learning step (the coarse learning step), these relations are attributed with the same relevance strength than the others of the same type. During the learning for individual relations, although some of them are attributed with lower strength, the available relevance feedback information is insufficient for their strength to be reduced drastically. A possible solution hes in the elimination of these relations as soon as they are identified to be irrelevant to the document collection (corresponding to no document). The se- cond problem is the determination of a reasonable threshold for keeping terms in expanded queries. A very high threshold value would keep very few terms, thus compromising the inferential power of the approach; but a very low value would result in a long query which is costly to evaluate. In our experiments, we used no threshold value in order to test the impact of the thesaurus when it is fully exploited. The expanded queries are very long, leading to high evaluation cost. Using a threshold would reduce the cost of query evaluation. Note finally that, although our approach has been described within a fuzzy modal logic framework, it is not incompatible with a probabilistic perspective. If term relevance relations were measured in terms of probability (as dependence probability), then the fuzzy framework should be replaced by a probabilistic framework. To do this, however, we would need to define a more strict inference rule in order to maintain consistency. 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Intelligent Systems: Approaches and Limitations Mario Radovan FET Pula, University of Rijeka, Preradovićeva 1/1, 52000 Pula, Croatia Phone: +385 52 23455 Fax: +385 52 212 034 E-mail: mradov@efpu.hr Keywords: intelligent systems, mind, cognition, language of thought, neural networks, cognitive models, simulation, computability Edited by: M. Gams Received: July 26, 1996 Revised: August 15, 1996 Accepted: September 4, 1996 An analysis of attitudes and approaches to the development of intelligent systems is given, arguing that (1) the classical and connectionist approaches can be conceived of as two levels of description of the same phenomenon, facing the same essential problems; (2) the language of science is inherently limited, and existing cognitive models cannot include the subjective dimension of the human mind; (3) there is no way to create a system that "really understands" without being personally involved with the proper attitudes and actions; and (4) we should tone down the requirements and expectations which are put before AI if we are to deal with realistic research projects and reasonable discourse. 1 Introduction A large part of the controversies concerning machine intelligence comes from the fact that we don't have clear and complete answers to the questions "What is machine?" and "What is intelligence?" (cf. [1, p. 1]). The present paper does riot offer precise answers to these questions, but aims to point out the essential impact of language on the controversies concerning AI. We discuss the strengths and limitations of various approaches and attitudes; in this context, we argue that the requirements which are set for AI should be essentially cut down if we don't want to miss the possible by stubbornly searching for the inconceivable. Let us start with a few typical positions concerning the relation between the human mind and machines. 1.1 Mind and Machine According to Goertzel, "there is no fundamental obstacle to the construction of intelligent computer programs". Goertzel holds that the argument for such a claim "is a simple and familiar one", and that it could be stated like this: (1) "humans are intelligent systems"; (2) humans are "systems governed by the equations of physics"; (3) "the equations of physics can be approximated, to within any degree of accuracy, by space and time discrete iterations that can be represented as Turing machine programs". From these premises, Goertzel concludes that "intelligent behavior can be simulated, to within any degree of accuracy, by Turing machine programs" [17, p. 470]. I find this argument rather vague because it seems to confuse certain essential things such as to be, to represent, and to be represented (or to be, to simulate, and to be simulated). Speaking of the "very idea" of artificial intelligence, Haugeland says: "The fundamental goal [of AI] ... is not merely to mimic intelligence or produce some clever fake. Not at all. AI wants only the genuine article: machines with minds, in the full and literal sense. ... Namely, we are, at root, computers ourselves" [20, p. 2). However, Haugeland doesn't offer convincing justification for this starting position. On the other hand, Searle declares: "I want to put a final nail in the coffin of the theory that the mind is a computer program" [25, p. xi]. I hold that Searle is right in insisting that the human mind is not "intrinsically a digital computer" [25, p. 208]. However, he neglects the pragmatic value of the computa- tional interpretation of the human mind in the context of our efforts to develop a useful initial model of the human cognitive system. Finally, Fetzer raises the question of the worth of the enterprise aiming at the ultimate goal of AI as stated by Haugeland in the above quotation; he says: "it seems to be worth asking whether the replication of the mental processes of human beings should be worth the time, expense, and effort that would be involved in building them. After all, we already know how to reproduce causal systems that possess the mental processes of human beings in ways that are cheaper, faster, and lots more fun" [11, p. 55]. There is a grain of wisdom in Fetzer's reflection; but nevertheless, let us note here that the method of production of the systems with mental processes, which Fetzer has in mind is, in fact, not so cheap, fast, and even not so much fun as it seems at the very beginning of the production process. I take such claims concerning the relation between the human mind and machine only as more or less successful rhetoric figures. Namely, by speaking in such a vague manner, everything can be interpreted as a machine while nothing can be proved to be intrinsically machine (not even computers, if seen on the "wrong level" of description). Hence, I hold that one of the basic tasks of artificial intelhgence should be to define in a more precise way the proper goals and language in which they are stated. Without them, a great part of the discussions will continue to belong to one of these three classes: vague speculations, unrealistic promises, and lamentations of failed expectations. 1.2 Intelligence Concerning the question of intelligence, we face similar problems. For example, it has been claimed that according to "the new approach" to AI, "to design an intelligent system, one has to give it all properties of intelligent creatures", among which belong "intentionality, consciousness and autonomy along with generality and adaptivity" [16, p. 483]. Gams rightly stresses that to obtain all that "will be much more difficult than previously expected" [16, p. 488]. However, I don't know who "previously expected" that to construct a machine with the above stated properties could be less difficult than anything in the world! Furthermore, it is true that "peo- ple in general tend to beheve that even animals can display certain aspects of intelligence", while on the other hand, although "machines can solve difficult formal problems which are often practically unsolvable even by humans and definitely unsolvable for all animals, they are still regarded as totally unintelligent" [16, p. 488]. However, the above requirements concerning consciousness and intentionality, together with the "general belief" concerning animal and machine intelligence, put AI in an extremely difficult position] namely, with such criteria it becomes virtually impossible to construct anything that would be at the same time "intelhgent" and "machine"! Such requirements are simply so strong that they render it impossible even to try to undertake any reasonable step toward something that could be accepted as a "first approximation" to an intelligent system. I hold that such an attitude towards AI is neither justified nor productive. This attitude could be compared with the claim that medicine has failed since it cannot cure death. Faced with such requirements, we are constrained to abandon the very Mea of constructing intelligent systems, or to change our criteria concerning the intelligence of artificial systems. In this context, I hold that as long as we don't know how we could construct a conscious artificial system (and we could hardly know that as long as we don't know even how natural consciousness comes about!), we should define the intelligence of an artificial system in a strictly behavioral fashion. In other words, if we insist that a chess program which can beat a chess grand master is nevertheless not intelhgent then not only do we not actually have intelhgent systems but we also don't have any idea how we could construct one. The criticisms of the results and possibilities of AI primarily concern the classical symbolic information processing (SIP) approach. That approach to AI follows the tradition of Western thought which holds that to understand/construct something we must have a theory. In that context, to produce an artificial intelhgent system one is supposed first to find out the basic elements and laws of the natural intelligent (sub)system which one intends to rephcate, and then represent that knowledge in a formal language/system which can be suitably implemented on a computer. The first attempts of this kind were hmited to selected micro-worlds i.e. to selected subsystems of human cognitive abilities. But it turned out that (1) the intelligence of such systems — which did not have a large amount of common-sense knowledge — was essentially limited, and (2) that the very possibility of formal representation of common-sense knowledge was highly problematic [27], [7]. However, there are claims that the connectionist approach with its artificial neural networks (ANN) constitutes a new, more promising approach to the development of intelligent systems. The connectionist approach departs from the theory-oriented tradition of Western thought and attempts to replicate intelhgent behaviour without its exphcit formal description of that behaviour. Hubert and Stuart Dreyfus say that the connectionist approach "may show that Heidegger, later Wittgenstein and Rosenblatt were right in thinking that we behave intelligently in the world without having a theory of that world". However, the existing ANN systems are still very hmited, so that "the same common-sense knowledge problem, which has blocked the progress of symbolic representation techniques for fifteen years, may be looming on the neural net horizon" [10, pp. 438-39]. Finally, with ANN we meet the same problem as with SIP: namely, if an ANN system is to reach real intelligence, it is supposed that it must also "share our needs, desires, and emotions and have a human-like body with the same physical movements, abilities and possible injures" [10, p. 440]; let us add here that it should be also conscious of its own approaching death. In short, with ANNs we arrive at the same too strong requirements: too strong to permit us even to try to do anything in the direction of their realisation. Let as now turn to more concrete problems; we start with an analysis of the levels of description of digital computer (as a symbolic machine) and the human cognitive system; we then analyze the strengths and weaknesses of the SIP and ANN approaches to cognition and to the development of the intelligent systems. 2 Levels of Description To describe a phenomenon, one needs a conceptual system; for describing the human cognitive system, the taxonomy of the classical computer system has been taken as a starting model. Com- puter systems can be described at different levels of abstraction] following Winograd and Flores, let us introduce these five levels of description. - Physical level—At this level, the computer is seen as a set of elements which operate according to the laws of physics. There are no "symbols" or "operations" on this level: at best, there are only signals described in terms of laws of physics. - Logical level—At this level, the system is seen as a network of logical gates ("and", "or", "not" gates); here, the system can be described by some binary language. - Representation level—The level of the symbolic machine language (assembler); at this level, strings of binary signals are interpreted as symbols and operators. - Communication level—The level of programming/query languages by means of which the user exchanges data and instructions/requests with the system. - Situation level—The level at which an activity of the system is interpreted as solving a problem/task. These levels of description are introduced in accordance with pragmatic needs, and none of them pretend to show the true structure of reality by itself. Let us now try to define an analogous many-level model of the human cognitive system: - Physical level—The level of neuroanatomy; it shows the material and structural aspects of the human neural system. - Logical level—The level of neurophysiology; it shows the neural system as a network of functionally described neurons. - Representation level—This is the controversial point of the model; to follow the computer model, we should assume the existence of some a kind of "assembler" in the human brain. The best known proposal of such an assembler is Fodor's Language of Thought [13]; we deal with it in the next section. - Communication level—The level of natural language communication and reasoning; in keeping with the dominant terminology, we shall often call it linguistic level. — Situation level—The level of understanding and of goal-directed activity. The levels of description are defined in functional terms, so that the system can be studied (and modelled) on one level of abstraction independently of its descriptions on other levels. The functional properties of a given level must not be inconsistent with the assumed functional properties of the adjacent levels below and above, but within this limitation they can be modelled in various ways. Furthermore, functionally defined systems are medium independent in the sense that they can be realised in any medium which allows the realisation of their functions. Consequently, if a proposed model allows the complete description of the human cognitive system, and if all the functions contained in the description are realisable by artificial means, it follows that the human cognitive system could be replicated in ways and media which are structurally and materially different from the human brain. Let us now consider the basic arguments concerning the validity of the five-level description model of cognitive system; the most controversial is the representation level, since the two levels below it are subjects of empirical research in the neuroscience, while the two levels above it seem to be determined by it. 3 The Classical Approach This approach to cognitiori tries to describe (and replicate) human cognitive abilities by following the model of computer systems given in section (2). In this context, the representation level (i.e. the level of "machine language") seems to be of essential importance, since it is supposed that if we could describe/rephcate the human cognitive system on that level, it should be relatively easy to obtain also the two higher levels, i.e. the level of communication and the level of understanding. The language of thought has been taken to be the "machine language" of the human cognitive system. 3.1 Language of Thought Fodor's Language of Thought (or Mentalese) is well known as a concept but not so well under- stood as a model of the human mind; hence, let us try to put forward the essentials of Fodor's proposal, We say that thoughts do not depend on any particular natural language because the same thought can be (or could be, by some coherent extensions) expressed in various natural languages. On the other hand, the linguistic abilities of speakers of different natural languages have the same structural properties. These two assumptions taken together make plausible the idea that the human cognitive system contains an internal lower-level language (innate and common to all humans), in terms of which the cognitive processes take place, while natural languages are only communication shells of the system. This internal language (comparable with assembly language) has been called the Language of Thought (LOT). The best way to find out what the hypothetical LOT level of the cognitive system should look like is to start from the outer (natural language) level of the system, and proceed by the following line of thought: a) Human linguistic abilities are characterised by certain structural properties. b) Sentences of natural language express/mirror thoughts. c) Therefore, the cognitive abilities should have the same structural properties. d) LOT is such a formal system which offers the best explanation of these structural properties. According to Fodor and Pylyshyn, the basic structural properties of human linguistic abilities are: productivity, systematicity, compositio-nahty, and inferential coherence. The principle of productivity says that humans can (in principle) produce an unlimited number of different sentences. By systematicity it is meant that a speaker's ability to produce and understand some sentences imphes the ability to also produce/understand certain other sentences. The principle of composi-tionality says that lexical items of natural language make nearly the same semantic contribution to each sentence in which they occur, which means that they are context-independent. By inferential coherence it is meant that in natural languages, the syntax and semantics of composed assertions mirror one another. (For example, the truth of an assertion of the form 'P and Q' implies the truth of the assertion 'P' and the truth of the assertion 'Q', and vice versa.) All these structural properties can be best explained by assuming a representational and combinatorial nature of the linguistic system. The concept of "representational nature" says that language units represent entities (in the world), while "combinatorial nature" says that validity/meaning of complex linguistic units is defined in terms of — and can be computed from — the vahdity/meaning of their constituent parts. In accordance with the starting position concerning the relation between the structural properties of linguistic abilities and the underlying abihties to think, it has been assumed that at some thought-producing level the human cognitive system could be defined as a representational and combinatorial system: therefore, that it could be described by a kind of representation language of the combinatorial syntax/semantics. LOT is taken to be that language; with this, LOT figures as the source and explanation of the initial four structural properties of the human hnguistic abilities. The LOT hypothesis further holds that: a) The states of some "points" of the brain form the representation of some proposition, and with it a representation of some state in the world. b) Propositions are composite entities; the same holds for their mental representations: they are composed of mental atoms, the minimal content-bearers. c) Tokens (i.e. physical items/signs in the brain) which record the same content are of the same form/type: that form is the mental symbol of that specific semantic content. d) There is a coherent relation between the syntax/form level and the semantic/content level of the combinatorial operations which take part in LOT seen as formal system. The LOT hypothesis doesn't say anything about the exact forms and contents of mental atoms. But starting from the asswmecJ existence of such minimal representation items of fixed syntax and semantics, it offers an explanation of the reasoning processes. In a nutshell, the LOT hypothesis claims that the syntactic properties of a representation item can be reduced to its shape, a physical property. This further means that causal interactions of tokens (which depend on their physical properties) are determined by syntactic properties of the mental symbols which they token. Fodor says: "the syntax of the symbols might determine the causes and effects of its toke-nings in much the way that the geometry of a key determines which locks it will open" [14, pp. 1819]. It means that although the physical properties "onto which the structure of the symbols is mapped" are those that "cause the system to behave as it does" [15, p. 14], the human cognitive system can be conceived as an automated symbol system. In that context, the cognitive process can be equally seen as causal sequences of tokenings (of mental symbols) and as formal (rule-driven) symbol manipulation. LOT is the core element of the classical/SIP theory of cognition. To complete the theory, Fodor also introduced a set of functional "boxes", which can be described as special-purpose processors. For example, to believe that P means to have a token of the mental symbol 'P' in the belief box, and to hope that P means to have a token of the same mental symbol in the hope box, and so on, "a box for every attitude that you can bear toward a proposition" [14, p. 17]. And for actions, there is an intention box-, when you intend to make it true that P (i.e. do/make what 'P' says), you put into the intention box a token of the mental symbol for P; the box then "churns and gurgles and computes and causes, and the outcome is that you behave in a way that (ceteris paribus) makes it true that P" [14, p. 136]. The LOT based model of the human cognitive system is a hypothesis, and as every hypothesis it should be evaluated on the ground of its explanatory power and its pragmatic effects. Many hold that the SIP model (based on the LOT hypothesis) is the best theory of cognition we have, and Fodor claims that "the cost of not having a Language of Thought is not having a theory of thinking" [14, p. 147]. However, there are also opponents of the computational approach to cognition in general, and of the LOT hypothesis in particular. Searle, for example, says: "The brain produces the conscious states that are occurring in you and me right now ... But that is it. Where the mind is concerned, that is the end of the story. There are brute, bhnd, neurophysiological processes and there is consciousness, but there is nothing else ... no mental information processing, ..., no language of thought, and no universal grammar" [25, pp. 228-9]. Searle's position doesn't seem coherent to me. Namely, every theory/model implicitly imposes some structure onto Reality; LOT does this, but so does neurophysiology. It could be a psychological fact that by approaching the level of the physical we feel as if we were approaching Truth/Reality, but that is only an illusion: science is a pragmatic enterprise, and all theories are in essence only hypotheses. 3.2 Objections to SIP/LOT The first objection to the SIP approach says that it simply projects the model of thè Turing/von Neumann machine onto the realm of the (mysterious) human cognitive system. That is largely true, but it doesn't say much about the explanatory and operational value of the SIP approach. Namely, such tentative projections from the known to the unknown (felt to be "structurally similar" to the known) are not exceptions in science but the rule, especially in the initial phase of an inquiry. However, it is true that whenever the advocates of SIP need some "box" to complete the model, they simply borrow it from the computer model: and that "solution" could be too easy solution, often grounded only in that need. One of the essential objections to the LOT hypothesis concerns the mental atoms understood as basic context-independent content bearers upon which computational operations are performed. For example, Clark says that the LOT hypothesis is "false" because the "folk solids" (i.e. natural language concepts/propositions) do not have inner mental representations "in the form of context-free syntactic items" [5, p. 13]. Furthermore, the LOT hypothesis assumes the existence of a fixed and innate set of types of mental atoms: we are supposed to work with a fixed repertoire of basic elements, so that any content a human could ever learn, imagine or express should be created (and represented) only by recombination of innate mental contents. That is a strong hmitation, because it does not allow the expansion of the initial representation power of the cognitive system. Finally, the very idea of an innate and fixed set of types of basic cognitive items has been qualified as "fundamentally alien" to results in developmental psychology [18, p. 408]. The main weakness of the LOT hypothesis (and of SIP), taken as an explanation of human cognitive abilities, concerns the semantics of mental atoms. A LOT-based system is a model of the internal level of the human cognitive system. Now, in order to parallel the syntax/semantic coherence of the outer (linguistic) level, the LOT system cannot be merely a syntactic engine, because such systems can generate only new meaningless marks from the existing ones. To pass from marks to thoughts/meanings, the LOT hypothesis must hold that representation items have not only fixed forms, but also innate fixed meanings. This step deserves a little more attention; namely, by assigning semantic properties to LOT atoms, Fodor has, in fact, "solved" the perennial mind-body problemi A transcendental justification for such an assumption is simple: (1) if thoughts have meanings, then meanings must come from somewhere; (2) let us take it that they come from the semantic properties of the basic mental items. Within Fo-dor's model, such an argument could suffice, but it makes the model rather speculative; still useful as a working hypothesis in AI, but of limited value as an explanation of the human cognitive abihties. However, let us note that adherents of the SIP approach are, in fact, not even supposed to answer what makes the atomic items have semantic properties. The SIP approach is defined in functional terms: it assumes the existence of a set of "basic building blocks" out of which all other items and explanations are constructed, but which are by definition cognitively impenetrable. In other words, by having no way to ehminate the perennial gap between the objective and the subjective, the SIP/LOT approach simply "bridges" it by an assumption which "works" inside the model, but nobody knows how. One of the objections to the SIP approach concerns the disproportion between the rapidity of some complex cognitive processes and the slowness of the underlying neural operations in the human brain. It has been argued that such rapidity on the hnguistic and situation levels of the cognitive system wouldn't be possible (with such a slow neural system), if cognitive processes had the SIP internal structure. But rapid cognitive processes (e.g. fast understanding of complex situations, or face recognition) exist: therefore, the SIP hypothesis must be false. To such objections the classicists reply that SIP is not concerned with neural operations (i.e. with the physical and logical level of the system, as defined in section 2); consequently, they can accept that cognitive processes are going on in parallel (and so remove the speed objection), but still coherently claim that cognition itself should be conceived as symbol-processing. Let us note that such a reply virtually cannot be refuted; however, it reduces the SIP position to the mere insistence that cognition is essentially symbol-processing. 3.3 Plausibility of SIP/LOT It is often claimed that SIP (with LOT) is the best paradigm we have in the scope of cognitive science. The plausibility of SIP/LOT has been also acknowledged by more cautious authors, and even by opponents. For example, Cummnis holds that although the ways of tokening of symbolic data structures (in the brain) are still not known in detail, SIP "has demonstrated the physical in-stantiabihty of such structures and has made ... progress toward demonstrating that at least some cognitive processes can be understood as symbol manipulation" [8, p. 13]. On the other hand, Clark, as one of the opponents of the LOT hypothesis, says that "no one knows" if "human cognition exploits, at least at times, a classically structured text-hke symbol system" [5, p. 227]; but elsewhere Clark admits that "something a bit like a language of thought may exist" [18, p. 411]. However, Clark holds that LOT is at best "the symbolic problem-solving tip of a large ... iceberg"; and beneath the symbolic level "lie the larger, less well-defined shapes of our basic cognitive processes": and only the understanding of these processes would "address the fundamentals of cognition" [5, p. 227]. 4 The Connectionist Approach While the classical approach starts from human linguistic and inference abihties, connectionists aim to develop systems with cognitive abilities by following the human brain structure at the neural level. Some (rather uncritical) adherents of this approach claim that "the neurocomputatio-nal alternative promises to provide some solutions where the older [classical] view provided only problems" [4, p. 252]. 4.1 Artificial Neural Networks Adherents of the connectionist approach tend to speak of ANNs as panacea for nearly all problems (see e.g. [4]); let us put forward the essentials of this approach. An ANN consists of a set of interconnected units (nodes), typically divided into three subsets: (1) input units which receive information from the environment, (2) output units which display the result, and (3) hidden units which mediate the spread of activation between input and output units. A node is characterised by a variable representing its level of activation and by a constant representing its threshold: when the input activation of a node exceeds its threshold, activation propagates to the other nodes with which that node is connected. Links are weighted, with weights determining the relative quantity of activation they may carry. An input to the network is a vector of signals (a "pattern of activation values") clamped on input nodes (to every node a value). Triggered by the input, activations spread throughout the network in a way determined by the input pattern, node thresholds, links, and weights of the links. The output of the system is the vector formed of the activation values of the output nodes when the network settles down into a steady state [see 7, 2, 4, 5, 8]. ANNs are also called vector transformation systems. An ANN acquires knowledge by being trained on a set of examples. The system typically starts with a random distribution of unit thresholds and weights. After every exposure to a training exemplar, activations (states) of the output units are compared with the desired output pattern, and the weights/thresholds of the units are gradually changed until the output pattern (for the given input exemplar) becomes equal to the desired one. The same process is repeated with each training exemplar. Adjustments made during training with one exemplar may distort the knowledge acquired through former training exemplars, so that the training process must be cychcally repeated until the network reaches a thresholds/weights configuration which correctly transforms all the exemplars from the training set. It is said that the training process "extracts the statistical central tendency" of the training exemplars, forming with it a ^^prototype-style knowledge representation" of the characteristic features of the exemplars [5, p. 20]. An ANN system shows its knowledge (acquired by training) when it is requested to process/transform new inputs of the same type as those with which it was trained. ANNs are characterised by holistic knowledge storing: any piece of knowledge could be distributed throughout the network, so that every node can take part in the encoding of any piece of knowledge contained in the network. In ANNs there are no context-independent data records which could be said to represent natural language semantic units (concepts and propositions): every node can be said to encode many things, but it represents no particular thing. 4.2 Objections to ANNs The two basic problems with ANNs concern the representation of input/output data (because not all data can be easily/suitably stated in vector form), and especially the lack of effective learning algorithms which could decide which weights/thresholds should be changed and how. Without satisfactory solutions to these two problems, every excessive enthusiasm with the con-nectionist approach seems completely ungrounded. Fodor and Pylyshyn argue that the connec-tionist model cannot explain the basic structural properties of the human hnguistic and cognitive abihties, such as productivity, systematicity, compositionahty and inferential coherence. This objection concerns the very idea of the connecti-onist approach, independently of the problem of learning algorithms. "Nothing in my treatment is sufficient to fully exorcise the ghost of Fodorian systematicity", says Clark; however, he believes that "the way forward is simply to bracket the problem" and to "pursue the connectionist paradigm for all it is worth" [5, p. 224]. Whereas an ANN acquires knowledge only by being trained with an appropriate set of exemplars, humans have the abihty of virtually instantaneous learning of an expHcitly given rule, and of its immediate application. Hadley offers a simple but effective example; consider the phrase "love ever keeps trying", and the rule, "Proceeding from left to right, mentally extract the second letter from each word and concatenate these letters in sequence" [19, p. 185]. A human of average cognitive abilities can immediately acquire and apply such a rule, even if he has not encountered the rule and the data before. This diminishes the plausibility that the connectionist method of knowledge acquisition (cyclic training to gradually tune the network) could be the method by which humans learn rules. One of the side effects of holistic knowledge representation is the vulnerability of stored knowledge to new training inputs: if one tries to store some new knowledge into an already trained network (by training it with a new set of exemplars), it can happen that the new adjustments of the thresholds/weights blank out the old knowledge. In such a case, all training exemplars must be "cycled past the net again and again, so it is forced to finds an orchestration of weights which can fit all the inputs" [5, 146]. Nothing of that kind happens to humans. Holistic knowledge representation also runs counter to the common-sense idea of how we know/store a fact, for example, that a cat has a tail. We usually suppose that such knowledge should be recorded somewhere in our brain as a kind of fixed record which stands there for years: but there are no fixed records in the connectionist systems. Finally, connectionists have essential problems with the explanation of their results. Namely, in science it is generally not enough to construct a system which gives some results; the results should also be accompanied by a causal explanation of how they have been obtained. However, by renouncing symbols and rules, connectionism has deprived itself of means by which such explanations could be formed: hence, it must borrow "ahen" explanatory means to even qualify as a scientific activity. Techniques such as cluster analysis, by means of which one can generate a "static symboHc description of a network's knowledge" have been used [5, p. 33]. Such descriptions do not mean that symbols (which they use) exist as context-independent syntactic items in the network: they are only post-hoc semantic explications of what the network knows/does, and not of what is going on inside the network. In sum, concerning the problem of explanation, the connectionist approach is "both sound and problematic", as Clark rightly observes: it is sound because it avoids projecting a coarse symbohc language onto the cognitive mechanism itself; it is problematic because, by the same token, it deprives itself of explanatory means [5, p. 67]. 4.3 Plausibility of ANNs There are many skills which humans acquire (and exercise) by training, and virtually unconsciously. Such skills — for example, riding a bicycle — do not consist in verbal knowledge, and their exercise does not require explicit rule-driven reasoning; moreover, we usually cannot even describe them in verbal/symbolic form. Consequently, it is claimed that the knowledge of such skills should not be stored in linguistic/symbolic form (so the SIP/LOT approach could not offer a satisfactory description). Humans acquire such skills by practice: therefore, some training-based model could lead us to the understanding of the cognitive background of such skills, or at least to their successful simulation. This is the strongest argument for the connectionist approach. Connectionists stress the structural similarities between the ANNs and the neural networks of the human brain. However, this argument is not decisive because actual ANN systems are quantitatively very much smaller than the human brain, and qualitatively, they are only a "crudest approximation to networks of real neurons" so that they cannot actually offer "any real insight into how the brain functions" [7, p. 222]; consequently, the alleged similarity is still very coarse. It is often argued that the connectionist approach should confine itself to the level of physical implementation (the level of "hardware") of the cognitive system. Reduced to that level, connec-tionism would not be a cognitive theory, but only an implementational model for the SIP theory of cognition. However, Fodor and Pylyshyn, although adherents of the SIP approach, point out that connectionist systems could be suitable in those cases where "empirical considerations suggest detailed structure/function correspondences ... between different levels of a system's organisation. For example, the input to the most peripheral stages of vision and motor control must be specified in terms of anatomically projected patterns ... Thus, at these stages it is reasonable to expect an anatomically distributed structure to be reflected by a distributed functional architecture" [15, p. 63]. In other words, independently of its (un)suitability for hardware implementation of the SIP model, connectionism could be the right approach to the development of peripheral units within a global SIP-oriented model of the human cognitive system. 5 Cognition and Computation: the Limits The models of the human cognitive system which we discussed do not say much (if anything) about the rule of the subjective side of cognition nor about subjective mental states in general. Let as now put forward some of the fundamental problems focusing upon the formalizability and expressibility of knowledge and subjective mental states. 5.1 Limits of the Computable We have discussed the methodological and episte-mic differences between the classical and connectionist approaches: but is there any deeper, onto-logical, difference between these two? Many hold that there should be, but it is hard to say what it consists in. Namely, every ANN can (in principle) be simulated on a SIP system, and every SIP system can (in principle) be simulated by a set of specialised ANNs (e.g. every basic function of the SIP system is simulated by an ANN). Therefore, the two cognitive models have the same expressive power. Indeed, we have already argued that they describe the same phenomenon on two different levels, and that they can be generally conceived of as the "hardware" and the "software" descriptions of the same system. Computers, as symbol systems, are said to simulate (some of) the human cognitive abilities. However, some claim that symbol systems cannot acquire any real cognitive ability. A symbol system can only manipulate that knowledge which can be expressed in some symbohc language; and it has been argued that human knowledge cannot be stated in purely linguistic form. Winograd and Flores hold that the two essentials of the human cognitive situation are: a man is always already situated in some cognitive background which cannot be explicated (and hence not formalised) b knowledge consists in concernful action ("care", in Heideggerian terms) and not in mere information possessing (neither in SIP nor in ANN fashion). According to the Background hypothesis, the meaning of an expression is always the result of its interpretation against some given background; the unspoken (background) determines the meaning more than what has been said. "Every explicit representation of knowledge", says Winograd, "bears within it a background of cultural orientation that does not appear as explicit claims, but is manifest in the very terms in which the "facts" are expressed and in the judgment of what constitutes a fact" [26, p. 453]. An attempt to explicate all the content of the background would be not only endless but also useless because assertions without any background have no meanings at all [see 24]. Consequently, the category of meaning is not applicable inside formal systems because symbol manipulation, by itself, without an outer interpreter, is simply senseless (and so is ANN vector transformation). On the other hand, according to the Care hypothesis, human communication is a form of concernful social action, and not mere transmission of information. Social action implies commitment: A normal human being cannot be said to understand an assertion (heard or said) without being somehow committed to its content. And to be committed, one must be somebody (must be an I), which an automated system is not: hence, automated systems cannot really understand. (Such claims challenge the classical approach, but since we don't see ontological differences between SIP and ANNs, we assume that they also equally challenge the connectionist approach.) On the basis of the Background and Care assumptions, Winograd and Flores claim that computers cannot even in principle acquire any real cognitive ability. Hence, human cognitive abilities could be neither explained nor replicated by any kind of computing system. In other words, human cognition cannot be reduced to mere computing, and even less could the conscious mind as a whole. Let us note that this line of reasoning rejects the independence of cognition from subjective mental states, which was one of the (often tacit) basic assumptions of cognitive science. I hold that Winograd and Flores are right, and that a Care-less automated system can neither communicate nor understand in the sense in which people do. And what about thinking and intelligence without understanding? With that, we return to the starting problem of how to evaluate (or speak of) the intelligence of artificial systems. As stated in section (1), we hold that the intelligence of such systems should be judged in a behavioral fashion (despite all drawbacks of such a decision). Epi-stemic and methodological changes which bring about the passage from SIP to ANNs are not the decisive step towards true understanding and intelligence. And we don't have any idea how the decisive step in that direction should look hke. Let us conclude with a comment on the CYC project started by Lenat in 1984 [21], with the aim to build a system whose knowledge would contain most of what humans call common-sense knowledge. ("CYC" is an abbreviation of encyclopedia; after some initial explicitly inserted amount of knowledge, the system was supposed to continue to learn automatically, from media such as books, newspaper, etc.) The CYC project follows the SIP approach; it uses explicit knowledge representation (by means of a formal language of sentential form) and an extensive formal inference system (with heuristics). It was thought that such a system could serve as the formaUzed common-sense background for expert systems of various kinds. Although the project is not fully completed, it has been claimed that CYC is not going to attain his mark (or that it has already missed it); for example, Michie holds that CYC has not attained "even the semblance of human-level knowledge and intelligence" [22, p. 464]. In the context of the Background and Care hypotheses stated above, I hold that such criticism, although perhaps premature, should be justified. However, I don't see what else could we do if not keep trying in the hope that, if not an artificial mind, we could at least design more efficient machines. 5.2 Limits of the Expressible The basic presupposition of science is that rea-Hty is objective in the sense that neither its existence nor its structure depend on the observer: to explain a phenomenon one has to describe it from the neutral (third-person) point of view. But the phenomenon of conscious mental state resists the neutral (non-personal) description beca- use such a state is essentially a personal/subjective state. The ontology of the mental is an intrinsically first-person ontology, says Searle [25, p. 95], and there is no place for first-person phenomena in the objective picture of the world. Following Searle's line of thought, one could speak of the ontological gap between the objective and the subjective (because the two are of radically different nature)] however, be it with ontology as it may, it seems obvious that our knowledge of these two kinds of facts are of a radically different nature: hence, I prefer to speak of the epistemic gap. There are attempts to eliminate the gap by reducing the mental to the physical. However, such attempts are bound to fail because reduction to the physical "dissolves the behaver as well as the behaviour. What's left is atoms and void" [14, p. 9]. And the taxonomy of "atoms and void" cannot express what it's like to be me: hence any possible story concerning me, told only in terms of "atoms and void", is incomplete. Researches in neurology indicate that the neural basis of conscious subjective mental states is to be found in certain 40 Hz neural oscillations [12, p. 130]. But how could a 40 Hz neural oscillation explain what it's like to be me? And it is certainly hke something to be me, and probably Hke something to be you, and maybe like something to be a bat, as Nagel would say. "Nothing in any future account of neural microstructure", says Cole, "will make perspicuous why that microactivity produces the subjective consciousness that it does" [6, p. 296]. In fact, the question is not so much "why" (or how) the subjective is produced, but what is that which the neural activity "produces", and how to speak of it. In sum, we have no clear idea how we should deal with subjective experience in an objective world: and we can hardly speak of artificial mind as long as we don't know how to deal with the natural one. Trapped between the ontologically monolithic scientific picture of the world and the intrinsically dualistic epistemic situation of the conscious subject, we are prone to speak of the mental in ways which could often be qualified as banal or incoherent, or both. That doesn't mean that the mental is completely intractable, but it does mean that our actual (and maybe possible) taxonomy and understanding of mental phenomena is essentially limited. In that context, decisive claims that humans are machi- nes, or that to become intelhgent, machines should share our needs, desire, and emotions, don't tell us so much (especially not in the operational sense) as it would seem at first sight. 6 Conclusion According to Copeland, the human mind "is coming to be seen as a rag bag ... of ad hoc tools assembled by Mother Programmer, the greatest pragmatist in the universe" [7, p. 241]. However, we should not mix the pragmatism of Mother Nature with the lack of clarity in our descriptions of its products. In other words, we should recognise at least the following: (1) that there are limitations inherent to the objective language of science; (2) that the actual cognitive models are essentially limited because they don't include the subjective dimension of the conscious human mind; (3) that we don't see how to create a system that could "really understand" without being conscious (and personally involved) in the world; (4) that the classical and connectionist approaches belong to different levels of description of the same phenomenon (and hence must face the same basic problem); (5) that we are constrained to Hmit the requirements and expectations of AI if we are to deal with realistic projects and reasonable discourse in that scope. References [1] Bojadžiev, D.: 'Godel's Theorems for Minds and Computers', Informatica, Vol. 19 (1995), pp. 627-634. [2] Butler, K.: 'Neural Constrains in Cognitive Science', Mind and Machines, Vol. 4 (1994), pp. 129-162. [3] M. P. Churchland: A Neurocomputational Perspective: The Nature of Mind and the Structure of Science, The MIT Press, 1992. [4] Churchland, M. P.: The Engine of Reason, the Seat of the Soul, The MIT Press, 1995. [5] A. Clark: Associative Engines: Connectio-nism, Concepts, and Representational Change, The MIT Press, 1993. [6] Cole, D.: 'Thought and Qualia', Mind and Machines, Vol. 4 (1994), pp. 283-302. [7] Copeland, J.: Artificial Intelligence: A Philosophical Introduction, Blackwell, 1993. [8] Cummnis, R.: Meaning and Mental Representation, The MIT Press, 1989. [9] D. C. Dennett: Consciousness Explained, Penguin Books, 1993. [10] Dreyfus, L. H., Dreyfus, E. S.: 'Making a Mind vs. Modeling the Brain: AI Back at a Branchpoint', Informatica, Vol. 19 (1995), pp. 425-441. [11] Fetzer, J. H.: Artificial Intelligence: Its Scope and Limits, Kluwer Academic Publishers, 1990. [12] O. Flanagan: Consciousness Reconsidered, The MIT Press, 1992. [13] Fodor, J. A.: Language of Thought, Harvard University Press, 1975. 14] Fodor, J. A.: Psychosemantics, The MIT Press, 1987. [15] Fodor, J. A., Pylyshyn, Z. W: 'Connectio-nism and cognitive architecture: A critical analysis', Cognition, Vol. 28 (1988), pp. 3-71. [16] Gams, M.: 'Strong vs. Weak AI', Informatica, Vol. 19 (1995), pp. 479-493. [17] Goertzel, B.: 'Artificial Selfhood: The Path to True AI', Informatica, Vol. 19 (1995), pp. 469-477. [18] Guttenplan, S.: A Companion to the Philosophy of Mind, Blackwell, 1994. [19] Hadley, R. F.: 'Connectionism, Explicit Rules, and SymboHc Manipulation', Mind and Machines, Vol. 3 (1993), pp. 183-200. [20] Haugeland, J.: Artificial Intelligence: The Very Idea, The MIT Press, 1986. [21] Lenat, D. B., Guha, R. V.: Building Large Knowledge-Based Systems, Addison-Wesley, 1989. [22] Michie, D.: '"Strong AI": an Adolescent Disorder', Informatica, Vol. 19 (1995), pp. 461468. [23] Nagel, T.: The View from Nowhere, Oxford University Press, 1986. [24] Radovan, M.: 'On the Computational Model of the Mind', Informatica, Vol. 19 (1995), pp. 635-645. [25] J. Searle: The Rediscovery of the Mind, The MIT Press, 1992. [26] Winograd, T.: 'Thinking Machines: Can There be? Are We?', Informatica, Vol. 19 (1995), pp. 443-459. [27] Winograd, T., Flores, F.: Understanding Computers and Cognition, Addison-Wesley, 1987. Informational Transition of the Form a\= ß and Its Decomposition Anton P. Zeleznikar An Active Member of the New York Academy of Sciences Volaričeva ulica 8 1111 Ljubljana, Slovenia (anton.p.zeleznikar@ijs.si) Keywords: causality, cause-effect philosophy; circular and metaphysicalistic transition a j= a; decomposition: canonic, noncanonic, serial, parallel, circular-serial, circular-parallel, metaphysicalistic-serial, metaphysicalistic-parallel; demarcated: frame, gestalt; informational: circle, graph, gestalt, transition a [= ß\ metaphysicalistic: circle, graph, gestalt; number of the transitional decompositions: possible, canonic, noncanonic; parenthesized: frame, gestalt; transitional decomposition Edited by: Vladimir A. Fomichov Received: December 27, 1995 Revised: February 22, 1996 Accepted: March 5, 1996 In this paper the complexity and heterogeneity of informational transition occurring between informational entities is studied to some formalistic details, using the technique of informational decomposition [6, 7, 9, 10, 11]. E. Birnbaum [1] has reopened an important problem of the informational theory by a formulation of the informa,tional-causal chain. General informational theory can substantially concern this particular problem, that is, studying the decomposition possibilities of formula a\= ß and its circular, particularly, metaphysical case a \= a. In this paper, the decomposition problems of both a\= ß and a\= OL will be generalized and concretized in the form of several informational systems, which appear to be serial, parallel, circular-serial, circular-parallel, metaphysicalistic-serial, and metaphysicalistic-parallel, but also canonic and noncanonic. Among others, these formula systems are studied by the methodology of informational frames and gestalts [11] showing the possibilities of decomposition. At the end, a case of the social informational transition and its decomposition is discussed to some principled details. 1 Introduction problem of information transfer (transmission, distribution, broadcasting, receiving), in the form Informational transition^ belongs to the basic and of the disturbance-influenced triad, consisting of most important concepts of the general informa- the signal (or information) transmitter (simulta- tional theory [1]. Thus, formula a\= ß, and its neously, the informational source), channel, and circular and metaphysicalistic occurrence a |= a, receiver, can be formally (symbolically, theoreti- presents the primordial informational problem cally) generaUzed by the concept of the informa- from which one can start the research of the fun- tional transition (the informer operand, opera- damental concepts of the emerging general infor- tor between the informer and observer, and the mational theory. In this context, particular cases observer operand). Informational transition con- of open and closed transition formulas can be tre- cerns not only the problem of information tran- ated as, for example, the externalism a |=, the smitting, channeHng, and receiving by machines, internalism |= ß, the metaphysicalism a |= a (or media, and living beings, but also the problem /? 1= /3), and the phenomenalism a |=; |= /?. of informational arising (emerging of interior and In a particular way, by Birnbaum [1] reopened exterior disturbances, impacts) within all transitional components in their spontaneity and circu- ^This paper is a private author's work and no part of framework of the informational seit may be used, reproduced or translated in any manner .,. , n-.r- , i c whatsoever without written permission except in the case "^l^sm and parallelism. Significant examples of of brief quotations embodied in critical articles. informational transition are the following: 1. Transmission and reception of information-carrying signals through a channel between the transmitter and receiver is a technical system with the goal to mediate the transmitted signal, as undisturbed (undistorted) as possible, to the receiver. In this way, along the channel, noise and other signal disturbances can appear modifying the originally transmitted signal. Another source of noise and disturbances can appear also in the receiver before the signal is converted (acoustically, visually, digitally or data-likely) for the purposes of various users (the problem of the receiver internalism, e.g., of the filtering of the arrived signal). 2. Another problem is, for instance, the writing down and shaping a message for the public distribution where the author gives his/her initial text to the inspection to his/her colleagues, correctors and editors, who perform in an informationally disturbing (correcting, lecturing) manner. Then, the corrected text is printed (with the removed "failures from the text form and contents"), and as such is distributed to other readers (in general, to the intelligent observers). Here, a strict distinction within the informational triad informer-mediator-observer is heavily possible in the sense of a strict separation of the informer, the correcting, editing and mediating channel, and the observer (individual reader, seer, listener, interpreter). The problem is also timely conditioned where the author could have already forgotten what he has written or even did not see his final result in the distribution medium. 3. Another example of informational transition happens in a live discourse, among several discursively interacting speakers, where more than one informer and observer interact in a speaking, listening (observing) and mediating informational environment. In this sense we can understand the informational decomposition of an initial theme which is thrown into a group of informational actors (speakers) and thus, at the end of the discussion, leaves different informational results (impressions) to the participating informational actors. 2 Technical and Theoretical Models of Information Transmission (Mediation) Technical model of information transmission or mediation proceeds from the well known triad transmitter-channel-receiver^. The idealistic case considers an informer, noise-free channel (mediator) and observer. The channel is commonly understood to be a transmission or propagation medium (an informationally active device) between transmitter (informer) and receiver (informer's observer). If information is carried in the form of modulated or coded electromagnetic signals and/or waves, the Maxwellian theory can be applied for the electronic circuits and electromagnetic waves to study the transmission and propagation possibilities in space and/or physical devices. Such a technical system concerns usually the reliable, true, or exact transmission (mediation) of signals. It does not concern the informational systems of living beings which do not exclude the arising of information on the side of informer, the propagation of information through the informin-gly active medium and the reception (understanding) of information on the side of informational observer. If the technical problem is first of all a genuine transmission (transfer) of signals irrespective of the loaded information, informational transition in general concerns informational emerging not only in the space and time of the informer but also in the space and time of the channel and the receptor, that is, the channel observer via which information is arriving. Therefore, the technical problem of information transmission is only a particular, purely technological problem within informational transmission. Technical problems of information transfer are more or less solved within determined technological systems where it is known under which circumstances these systems can function satisfactorily. ^The technical (telecommunicational) problem was mathematically formulated by Claude Shannon [4] where, as he said, meaning does not travel from a sender to a receiver. The only thing that travels are changes in some form of physical energy, which he called "signals". More important still, these changes in energy are signals only to those who have associated them with a code and are therefore able, as senders, to encode their meanings in them and, as receivers, to decode them [2], On the other side, the informational problems of transition, concerning spontaneous and circular information arising within of informationally living actors environments represent substantially ' different philosophy, methodology and formalism. Informational theory covers essentially this philosophy by a new sort of formalism, implicitly including the informational arising in a spontaneous and circular way. There does not exist a proper theory of this naturally conditioned problem of informing of informational entities. Contemporary philosophies seek their approaches and interpretations within the more or less classical philosophical orientations (doctrines of the so-called rationalism, especially cognitive sciences) performing within natural language discussions and debates and outside promising ways of new formalizations. 3 Information Transmission at the Presence of Noise Noise as an unforeseeable, spontaneous, chaotic and disturbing phenomenon remains in the realm of informational heterogeneity. A disturbing information does not only mean a distorted, useless or undesired phenomenon, but also the necessary and possible informational realm of changes, formations and origins, for example, in the form of the so-called counterinformation being a synonym for a spontaneously and circularly arising information, its informational generation as a consequence of occurring informational circumstances in space, time and also in brain. In this view, the informational noise carries the possibilities and necessities of informational emerging as a regular, desired or undesired, unforeseeable or expected informing of informational entities. Instead of information transmission at the presence of noise we can use a more general and also more adequate term called the transition of information in an informationally disturbing environment, where the spontaneously arising nature of informing of entities comes to the surface. Informational disturbance can be comprehended as a cause generating informational phenomenon from which informational consequences of various kinds are coming into existence. The arising mechanism of the informational roots also in the disturbing, causing and effecting (causing-to-come-into-informing) principles where disturbing is the phenomenon which rises the cause of the consequence. 4 Possible Informational Models of Transition On the introductory level, we can list and describe shortly the main informational models of transition, marked hy a ß. Some of this models are very basic and some of them can become more and more complex in a circular, recursive, also fractal^ manner and, certainly, in this respect, also spontaneous. The discussed models of transition a t= will be nothing else than informational decompositions (derivations, deductions, interpretations) concerning particular elements of the transition and the transition as a whole. So, let us list the most characteristic models of informational transition. 1. A decomposition of a /? can be begun by operator |= which becomes an initial operator frame [10, 11], that is. a N ß Usually, at the beginning, we introduce the so-called parenthesized operator frame and, the consequence of this choice is that the operator frame becomes spht, in general, into three parts, of the form (...( a N---N ß )...) where the ( ( and eft and the right parenthesis frames ) • • •) , alternatively, can be empty. 2. A more expressively compact form of the operator-decomposed transition is obtained by means of the so-called demarcated operator^ ^Fractal is a mathematically conceived curve such that any small part of it, enlarged, has the same statistical character as the original (B.B. Mandelbrot, 1975, in Les Objects Fractal). Sets and curves with the discordant dimensional behavior of fractals were introduced at the end of the 19th century by Georg Cantor and Karl Weierstrass. Parts of the snowflake curve, when magnified, are indistinguishable from the whole [12]. ^The so-called demarcation point, was introduced in metamathematics by Whitehead and Kussel [5], The privilege of such denotation is that the sequence of operands and operators in a formula remains unchanged, which does not hold for the Polish prefix or suffix transformation of formulas. A.P. Železnikar frame, where instead of each parenthesis pair with operator, that is, (■••)!= ^-^d |= (• • •)) one demarcation point is used, that is, • • •. |= and \= . • • - , respectively. The consequence of such notation is the disappearance of the parenthesis frames and, in this way, the appearance of only one unsplit operator frame in the decomposed transition (and also other) formulas. In general, the possible demarcated forms of the decomposed transition becomes a a 1= Wl . 1= ■ • • . 1= . Wi 1= . • • • 1= . Wn 1= ß] situation becomes clear when one imagines that the o-operator stands at the place of the main operator |= of a formula and that just this operator is split in the sense of 1= o |=, where the left (= belongs to |=Q.-decomposition and the right |= belongs to |=^-decomposition. 4. The next possibility of the informational transition decomposition is the one of the previous case when the parenthesized form is replaced by the demarcated one. In this situation, operator frames |=a and are not anymore split and the expression becomes compact and more transparent. Characteristic cases of such possibility are a 1= . ^ • • •. 1= a;„ . 1= o ^ /3; a . a;i • • ■ 1= . 1= ß a ha o H/3 ^ (...( a o ß )•••) a The first and the last operator frame do not include the demarcated form. |= . because the place of the main operator is at the end or at the beginning of the formula and operands ß (the first formula) and a (the last formula) are not parenthesized. Thus, the main informational operator 1= is in the first formula at its end and in the last formula at its beginning. 3. The next two examples concern informational transition a |= /3 in its form of operator composition, that is, 1= wi. 1= • . f= Wi . 1= t= .Wi+i 1= .■ ß-, In this way, simultaneously, to some extent, the meaning of the operator composition denoted by 1= o |=, comes to the surface. In this context, it can be decided, where the separation of operators |=a and \=ß actually occurs. The one separation point is certainly the composition operator 'o' and the other two are operands a and ß. One must not forget, that operator |=a is an informationally active attribute of operand a and similarly holds for operator in respect to operand ß. Let us decompose the parenthesized, operator-composed transitional form a |=aO ß. The general form will be where |=a and \=ß are split to the left parenthesis frame and the right parenthesis frame, respectively. Parenthesis frames can also be empty. This No operator frame does include the form . |= . (the place of the main operator of a formula) because this operator is hidden in the operator composition [= o |=. 5. The next question concerns the so-called circular transition. An informational entity, in itself, can function as a serial circular informational connection of its interior components which inform as any other regular informational entity. There is certainly possible to imagine an exterior circular informing in which a distinguished entity takes over the role to function as the main informational entity in a circle of informing entities. In principle, these circular situations do not differ substantially from the previous cases. The original informational transition a |= is replaced by the initial circular notation a\= a. There are various possibihties of studying decomposed circular transitions. For instance, in Fig. 2, there is a unique simple case of a transitional loop. Fig. 3 offers another interpretation, where to the serially decomposed loop there exists a parallel, yet non-decomposed circle. And lastly, in Fig. 5, the non-decomposed circular path can be replaced by the reversely decomposed first loop, bringing a senseful interpretation and informational examination of the first loop by the second one. 6. The next case provides an additional perturbation of the already decomposed components ui, ■ • •) ^n by means of some disturbing components 62, •••, èn, respectively, as shown in Fig. 10. These components impact the w-chain from the interior or the exterior. An interpretation of this disturbance is possible by means of parallel formulas, that is, h'^j] 3 = l,2,---,n This situation is studied in detail in Section 5.14 and represents an informational extension and theoretical interpretation of the case opened by Birnbaum in [1]. 7. Finally, there is possible to expand the basic decomposed informational decomposition with the initial components a;i, a;2, • • - , Wn in a fractal form as shown in Fig. 11. Thus, to the internal components wi, • • - , 't'n of the first transition similar other transitions take place in an unhmi-ted manner regarding the number of transitions. In this way, a complex transitional fractal is obtained consisting of variously connected informational transitions. In this way, the basic system of decomposed transition is extended by the additional system of informational formulas, that is, (• • ■ {{ai [= Ui^i) 1= a;j,2) h • ■ ■ Wi.ni-i) |= Sij Uij] 1= i = l,2,--sn; j = l,2,---,ni This formula system represents only a part of the graph interpretation in Fig. 11, not being presented in an informational gestalt form yet. 5 Serial, Parallel, and Circular Structure of Informational Transition Decomposition 5.1 Decomposition Possibilities Informational transition of the form ol\= ß can be decomposed in several informational ways— from the simplest to the most complex ones, but also in a serial, parallel, Circular, and metaphysi-calistic way. All components of transition a /3, that is, operands a and ß and operator |=, can be decomposed (analyzed, synthesized, interpreted) to an arbitrarily necessary or possible detail. By advancing of decomposition, informational boundaries between the occurring entities a, |=, and ß can become unclear and perplexed within the complexity of the structure which arises through various decomposition approaches. One of the basic problems is the systematiza-tion of decomposition possibilities (processes, entities) and their symbolic presentation. Decomposition of the general transition a\= ß 01 its me-taphysicalistic case a\= a can concern the serial, parallel, circular, metaphysicalistic, and any mixed case of the informational deconstruction of a 1= /3 and a\= a. Let us introduce the following general decomposition markers: f A_ (a 1= ß) serial i-decomposition A of a j= /? of serial length i (5.2); ^A||(q; ß) parallel decomposition A of a\= ß o{ parallel length I (5.8); • A^ {a 1= a) circular serial i-decomposition A of a 1= a of circular-serial length t (5.9); 1= a) circular parallel decomposition A of a 1= a of circular-parallel length I (5.11) where for subscript i (look at Subsubsection 5.12.6) there is 1 ' + 1 '2l\ V"- / Metaphysicalistic decomposition is specifically structured, that is, metaphysicalistically standardized. We introduce l'OR'^{a\=a) metaphysicalistic serial i-decomposition Tl of a |= a of circular-serial length i (5.12); 1= a) metaphysicalistic parallel decomposition 9JÌ of a 1= cc of circular-parallel length I (5.13) 5.2 A Serial Decomposition of a |= ß-, that is, [= ß) Let us start the decomposition process of transition a \= ß with the simplest and most usual serial case. Let us sketch this simple situation by the graph in Fig. 1. This figure is a simplifica- l^n-l Figure 1 : A simple graphical interpretation of informational transition a \= ß divided into the informer part (a), serially decomposed channel or internal part with informational structure of ui, ••• ; ^n, o-nd the observer part (ß). This graphical scheme represents the serial gestalt of a\= ß serial decomposition, that is, all possible serially parenthesized or demarcated forms of the length £ = n-\-l. The zig-zag path illustrates the discursive (spontaneous, alternative, also intentionally oriented) way of informing. ■■■ Un-2) N Un) h ß)\ Wt) N ■ • ■ ^n-2) 1= W„_l) 1= {Un t= ß)); n+2 V n+1 / (a \= (wi 1= (w2 1= (w3 1= • ■ • (wj 1= ■ • • H K-i N K h^))) •■•)■■■)))) where ^ is read as means or, also, informs meaningly. This conclusion delivers |=-operator decompositions oi a \= ß which, in the frame-parenthesized form [10, 11], are (•••((( N wi) 1= UJ2) \= wa) a 1= • ■ • cji) 1= • • • Un-2) 1= 1= Un) h ß-, tion of the model given by Fig. 1 in [1], On the other side, we have studied several forms of serial informational decomposition of informational entities and their transitions (e.g. in [6, 7, 9, 10]). The graph in Fig. 1 represents an informational gestalt [11] because various interpretations of it are possible. Let us interpret this graph in 'the most logical' manner. This interpretation roots in the understanding of technical systems where we conclude in the following way: - Transition a\= ß is understood as a process running from the left to the right side of the formula. We rarely take a [= /3, according to a parallel decomposition possibility, as a parallel process of components a, ß, and a ((...(...((( f= ui) t= U2) 1= U3) a \= ■■■Ui)\= ■■■Un-2) 1= ^n-l) t= \= ß ) 1= (Wi 1= {U2 1= {U3 a 1= • • • (wj 1= • • . {Un-2 1= {Un-1 \= {Un \= ß )))■••)•••))) More clarity could be brought to the surface by the use of the so-called frame-demarcated decomposition [11] which for the the first decomposition formula gives 1= . f= u;2. [= ■ a 1= •.. a;i • 1= • • • Un-2 ■ 1= Un-l . h ^^n . 1= ß — Processing from the left to the right, we come to the conclusion that the adequate informational formulas describing the internally structured decompositions of transition a \= ß are, according to Subsection 5.1, As we see, the operator decomposition in q; 1= is externally independent; there are only internal components by which the internal structure of operator is interpreted, that is, decomposed into details. The first formula is actually the strict informer ct's view of the transition phenomenon a |= /3. The strict observer ß's view of the transition phenomenon a\= ß is the last formula (a N ß) -den {a 1= (wi 1= (cj2 N ('^s 1= • • {uJn-2 t= (Wn-1 \= {(^n |= •)•••)))) The viewpoint of the observer ß proceeds systematically from the right to the left of the transition formula and so delivers a decomposed formula which, in respect to the positions of the parenthesis pairs, is structured in a mirrored form to the formula of the viewpoint of the informer®. The graph in Fig. 1 represents a gestalt belonging to any of its informational formula. Gestalt is a set of formulas which can be constructed for an informational graph. The strict informer and the observer viewpoint are only two possibihties: all the other are between the both. We will show how all formulas of a transition gestalt can be, to some extent, differently interpreted by the so-called operator composition |=q o \=ß. 5.3 A Transparent Scheme of the Canonic Serial Decomposition of ahß Let us introduce the general transparent scheme & of the canonic serial decomposition, marked by A^ (a 1= ß), in the form aUlU2U>3 ■ ■ • (Ji-iUi I UJi+iUJi+2 ■ ■ ■ this respect, there is interesting to mention, that some traditional impHcation axioms can be structured in a circular-observationaJ manner. E.g., the propositional axiom of consequent determination, A {B A), a,s the first axiom in different proposition and predicate calculi is identically true while {A ^ B) ^ A is not. aUlLU2^S ■ ■ ■ UJi-lUJiUi+lUi+2 ■ ■ ■ | ß; a I WlWaWa • • ■ OJì-iUJìUJìj^iLJìj^ì ■ ■ ■ Uln-2<^n-l'^nß where 0 < i < n Each underline marks one parenthesis pair at its ends, symbol marks the main operator (|=* or 1= ) of decomposition, and between two ope- rands (e.g., concatenation w^wi+i) an operator |= appears, according to the underlined formula segments. A serial decomposition is canonic if and only if its informer part is purely informer-canonic and its observer part is purely observer-canonic. For a serial decomposition of a /3 of length i — n + 1 there are exactly n + 1 canonic formulas. 5.4 Introducing Canonic Gestalt of Serial Decomposition of a\= ß Canonic gestalt F""" is a particular, reduced form of gestalt F, concerning an arbitrary serial decomposition of transition a |= /?, that is (also a non-canonic), "+jA_(Q: 1= ß), where l71,2 1= Wi) \=UJ2) N W3) 1= • • • Wi) ^ N ^n-l) \= \= {i^n \= ,ca„„,2 ß ) a can h "■"1=0 1= (W2 1= (W3 1= {Un-1 1= (Wn \= ß )))•■•)•■■)) can„ „ , canjl.n + l ( a \= (UJI \= {UJ2 \= (tja h • • • i^i N • •■N (Wn-1 1= (w„ 1= ß\))) ■■■)■■■))) ^cann.n+l Km To obtain the transparency of the last parenthesized formula, we can use the frame subscripts in the last formula, and CCrg"' where, for example, tt^ marks n + 1 — i consecutive symbols '(', tt^ marks j — 1 consecutive symbols ')', ma^rks the A;-corresponding operator frame on the left of composition operator 'o' and marks the /^-corresponding operator frame on the right of operator 'o'. Thus, for a compact presentation of the last formula we have (a o \=ß ß) 2 q TT ( TT/ ( C 71,71 I 71,n n TT, 0 ^^ ■ / or n 0 n—: 1 iT 0 ) One can introduce the parenthesis-canonic gestalt of the left parenthesis frames, for example, n-n where the replacement for the right-left or the left-right enumeration is n (T" f n—'. l (T" ( or respectively. Similarly, for the right parenthesis frames there is with the replacement concerning the right-left or the left-right enumeration respectively. In this way, the gestalt of the partial, main-operator composed, parenthesized left operator frame is The gestalt of the partial, main-operator composed, parenthesized right operator frame is The framed components can be recognized from the general parenthesized formula a\=a ° \=ß ß-This formula is a concatenation of the discussed parenthesis frames, main-operator composed left and right operator frames and the addressed informational operands a and ß in the form (a K a 1 o 1 ß 11) j Because of the parenthesis form of basic formulas, the last gestalt formula is split in several segments, which are the left parenthesis gestalt, operand a, the left operator gestalt, operator 'o', the right operator gestalt, operand ß, and the right parenthesis gestalt. To obtain a more compact expression of the formula where the left and the right operational frames are not split and can be, finally, also regularly vectored (in an operator-gestalt manner), we can A.P. Železnikar use the demarcated style of formula notation, that is, a ha °>|3 /? ■ — . a 1= wi. 1= a;2 . 1= . 1= • • • Wj . 1= ■ • • Un-2 . 1= Un-1 .\=Un.\= a 1= ■■■UJi.\= • • • ^n- -2 . 1= UJn-1 ■N -^^OK can„ 2 '.No a 1= . a;2 1= . u;3 1= . Un-l 1= . Wn f= N .LJl 1= . 0^2 1= . W3 a N N • • ■ . Wi 1= • • • . Un-2 ■^.1=0 N ' ^n-l 1= ■ ti^n 1= ^oN. ß .cann.n+l where In the last formula, there must be a strict correspondence between the elements of the enframed left and right operator gestalt in respect of the superscript i, where "■No 1= . f= W2 N ■ • • • ^n-i • 1= 1= can^ ^oN. 1= . CJn+2-i N ■ C^n+3-i ' " " N ■ '^n-l |= • a;„ |= The outmost frame is nothing else than the operand staying on the right of the operator of meaning, Formula is written in the consequent demarcated form where semicolons perform as separation markers between parallel formulas. To get an extremely compact expression of this formula, one can contract the occurring operator frames into two operator gestalts on the left and the right side of the composition symbol 'o', marked by r^p^ and respectively. Evidently, and Li)j for j < 0 and j > n does not exist. The symbolism concerning canonically decomposed gestalts and their formulas for transitional cases a j= ß and a\=a°\=ß ß is shown in Table 1. 5.7 Noncanonic Serial Decomposition of a [=ß, that is, |= ß) Both canonic and noncanonic serial decompositions constitute the realm of all possible serial decompositions of transition a\= ß. As one has learned, there are exactly Cn+i) possible decompositions of one and the same decomposition components ui,--- ,u>n, that is, of length n + 1. Noncanonic decompositions are exactly those which are not canonic, that is. n + 2 -h n + 1 (n + 1) and for the informational transition of the form « Na o N/3 finally, one obtains of them. Let us introduce the general transparent scheme © of the noncanonic serial decomposition, marked by |= /3), in the form Canonic Gestalts for (a h ß)-Decomposition Gestalt Formulas: i = 1,2,--- ,n-|-1 Canonic Gestalts for (a \=a o t=/3 ß)-Decomposition Gestalt Formulas: i ^ o\=o\=ß can „ j can„ can„ j ^a.\=o\=.ß nj^"" a r;;:^" n""" a rjf!," o \ a O ß n;^"" a ß a ^ aV-^oT-^ß Table 1: A systematic overview of possibilities (and possible markers) of the serially decomposed parenthesized and demarcated gestalts and framed formulas belonging to the informational transition a\= ß, where there are n decomposing operands, that is, transition-interior informational components ■ ■ -, f^n- A gestalt is a parallel system of n formulas consisting of different frames (f>... and operands a and ß. where the characteristic schemes of the pure ob-servingly structured informer part and the pure informingly structured observer part noncanonic decompositions are aLJiUJ2i03 ■ • ■ U>i-iUiU!i+iU!i+2 ' ' " | ß', e H ß)) - where n + 2n, and the observer part which is a itself. This graphical scheme represents the simplest gestalt of a\= a, that is, all possible serial parenthesized or demarcated forms of the length £ = n + 1. Formally, there is not a substantial difference between transitions a \= ß and a |= a and, for the circular case, where ß was replaced by a, operand a becomes the informer and, simultaneously, the observer of itself. The w-structure can be understood both to be its interior or interior informational structure or even a mixed interior-exterior structure. For us, the circular interior structure is significant in the so-called metaphysicalistic case. Further, if an u is an interior structure, the principles of informational Being-in [9] hold, so, a;i,W2, • • •, Wn C a Further, we must not forget the separation possibilities between the informing and the informed part of a. In the circular case, there is, a\=ao\=^a where the operator composition operator 'o' is a unique separator between the informing and the observing part of a. This informer-observer distinction becomes extremely significant in the metaphysicalistic case when, for instance, information produced by counterinforming of an intelligent entity a has to be informationally embedded, that is, observed and connected to the existing informational body of entity a. Thus, a circular informational structure is not only a trivial, nonsense, or an abstract entity: it has its own function of informational production and evaluation in the sense of spontaneous and circular informational arising, that is, changing, generating and amplifying the informational change. In circular informational structures, the problem of the informing and the observing part within a cychcally informing entity come to the surface. This problem is significant at the conceptualization (structure, design) of a circular informational entity. In principle, each entity informs also cyclically, for instance, preserving its form and content and changing it in an arisingly spontaneous an circular way. This principle belongs to the basic axioms of informing of entities (see, for example, [6, 8]). Let us proceed from the operand frame of the gestalt that is, of a circularly decomposed informational transition (n-l-2-i )-th h (Un+2-i \= ■■■ n+l—i i-1 Figure 3: Another graphical interpretation of the circular transition a 1= a, which is divided into the informer part (a), serially decomposed internal part with informational structure of uii, U2, • ■ -, ujn, and the observer part which is a itself in the decomposed path and, with the non-decomposed backward path. The framed operator, |= , is at the {n-\-2 - i)- th position of the framed formula and represents the so-called main formula operator, at the place where formula is split into the left informing part (informer a) and the right observing part (observer a). But, the framed operator, further split and, according to Tab previous discussion), there is, 1= , can be e 1 (and the TT, i = 1,2,--- ,n + l where partial frames tt^ ' , , 9^of=(' TT^ can be easily identified from the previous discussion. Thus, the separated informing and observing parts of circularly decomposed transition a a are n-l-l-i (n-(-2-i)-th 1= (w„+2-i 1= • • ■ h (^n-l N (^n f= « ) ■ • •)); j = 1,2,-•-,71-1-1 Another, shghtly modified graphical presentation in Fig. 3, following from Fig. 1 and Fig. 2, offers A.P. Železnikar I--{w^)-- ---(^n-l^-- Figure 4: The circular informational graph corresponding the graphical interpretation in Fig. 3. In an informational graph, the one and the same operand must appear only once (concerns a). an essential interpretation, namely, the parallelism of the w-decomposed path and the backward non-decomposed path a \= a. It does not represent the so-called informational graph in which each operand must appear only once. The correct informational graph is shown in Fig. 4. The formal parallel presentation of this graph is the formula system a 1= a; Q;|=WI; UJi\=ùJ2-, 012 1=^3; ijJi\=Ui+r, ••• 1= t^n-i; l^n-1 \= [= « using, entirely, the basic transitions only (from one operand to the other, or the same). 5.10 A Circular Forward and Backward Serial Decomposition of Informational Transition The problem of the circular forward and backward serial decomposition emerges in cases of the so-called metaphysicalistic informing when entities inform in an intelligent way and the question of the informing and the observing parts of entities becomes significant. In this situation, we have a general scheme of informing as shown in Fig. 5. Before we begin to discuss the circular and the reversely circular form of informational transition, let us construct Table 1 in which, in a surveying way, the operand and operator gestalts of different sorts, as the result of serial decomposition, are listed. In this table, the parenthesis gestalt are replaced pairs of the form ^nd by systematically marked pairs tt^ where tt, and TT / = 1.2. n + l. and TT z-1 for Figure 5: A graphical interpretation of the forward and backward circular transition a \= a, representing a parallel system of a forward and backward loop, being appropriate for an intelligent entity (e.g. forward and backward analysis and informational synthesis). 5.11 A Circular Parallel Decomposition of a 1= a, that is, ^ a) There is not an essential difference between parallel and circular parallel decomposition in respect to the formal informational scheme n+l A^ia h a) fai^uji] wi U2; \uJn \=a ) But, the essential difference occurs in the following: 1. 1= /?) is a circular parallel system of Figure 6: The bicircular informational graph corresponding to the graphical interpretation in Fig. 5. In an informational graph, the one and the same operand must appear only once (concerns a, ui, ■ • ■ consequently followed, the most basic transitions, between the initial informer operand a and the final observer operand, which is the same a; 2. 1= ß) represents the circular (serial) causal chain (decomposition) of consequently, in a circle followed operands a,uji, - ■ • ,ujn, and all from this decomposition derived decompositions belong to the circular gestalt r("+^A||5(a ß)), where the number of decompositions is ^^Cnti)' 3. \= ß) is the formal counterpart (equivalent) of the circular informational graph <5 (Fig. 2), by which all decompositions belonging to the informational gestalt r("+iAJj5(Q; 1= ß)) are determined. 5.12 Standardized Metaphysicalistic Serial Decomposition of a [= a, that is, ^-m^ia |= a) 5.12.1 Introduction Metaphysicalism means circular informing originating in the initial transition a\= a and its metaphysicalistic decomposition which, to some extent, was standardized [6] in a reductionistic manner. In this Subsection, our attention will concentrate on parenthesized, demarcated, normal and reverse cyclic, operator-compositional canonic and noncanonic metaphysicalistic informational decompositions and the corresponding gestalts. As we see, there is a couple of metaphysicalistic gestalts of a decomposed entity a which can be investigated from the standard metaphysicah-stically generalized and reasonably reductionistic point of view considering the variety of possible decompositions and gestalts. 5.12.2 Generalized Metaphysicalistic Decomposition of an Informational Entity Let a represent an informational entity concerning something ß. Let this entity be metaphysically decomposed in its serially connected but also in its parallel informing components: - informing components (superscript i) - counterinforming components (superscript c) and - informationally embedding components (superscript e) Besides, some circular forms of informing of involved metaphysicalistic components, including entity a, occur, thus obligatory, different loops exist regarding the metaphysicalistic components. Let this situation be concretized by the informational graph in Fig. 7. As a standardized (artificially constructed) situation, three substantial groups of an entity's metaphysicalism exist: intentional informing ensures the preservation (physical, mental, informational character) of the entity; counterinforming represents the emerging and essentially changing possibihties and character of entity's informing intention, so that the character of the entity can emerge and change as a consequence of the exterior and interior impacts concerning the entity; informational embedding is a sort of final acceptance and confirmation of the emerged and changed possibilities and state of the entity's character. A.P. Železnikar a's intentional informing a's counterinforming a;'s informational embedding Figure 7: A generalized metaphysicalism of entity a with interior informing, counterinforming and informational embedding, concerning something ß. Another comment of Fig. 7 concerns the loops of the informational graph. Six basic loops are recognized, however, this does not mean that in a concrete case additional loops between metaphysicalistic components can be introduced. The following principle seems reasonable: Principle of Metaphysicalism of Metaphysicalism. Components of a metaphysicalistic entity are, in principle, metaphysicalistic entities. Such a determination causes an endless fractalness of metaphysicalism (metaphysicalistic fractalism). □. Let us study some basic properties of the graph in Fig. 7. 5.12.3 Reductionistic Basic Metaphysicalistic Model of an Informational Entity Let us begin with the basic (most primitive) case, where the metaphysicalistic decompositional components of operand a within transition a j= a are ^Q! Cq, Ca, Cai ^c called 2. intention of the entity (its instantaneously arising character, concept, definition), 3. counterinforming (opposing, synonymous, antonymous, questioning intentional informing), 4. counterinformational entity (informational opposition, synonyms, antonyms, questions requiring answers as consequences of the intention), 5. embedding (the process of the connection of new information arisen by counterinforming, e.g., in the form of answering), and 6. embedding entity (information) by which new products are regularly connected with the existing informational body of the entity, respectively. These operands come at the places of the decomposition components tui, U2, ujs, UJ4, ws, and uq, in this order, so, n = 6 and the number of formulas in the canonic gestalt concerning solely the topic circular entity a is 7, in nonca-nonic gestalt 422, and altogether 429. The same number of formulas appear in gestalts belonging to the remaining six circular (metaphysicalistic) operands (components). 5.12.4 Canonic Metaphysicalistic (Reductionistic) Gestalts Let us construct the canonic (informer-observer regular) gestalts according to Table 1 on one side and, then, in the next Subsubsection, sketch the structure of and determine the number of the remaining noncanonic gestalts. There are the following cases of the reduced (standardized) canonic metaphysicalistic (the front superscript 'met') gestalts: 1. (intentional or entity's characteristic) informing, - metaphysicalistic, parenthesized reductionistic canonic gestalt (PRCG for short) - metaphysicalistic, demarcated reductionistic canonic gestalt (drcg) "" - metaphysicalistic, parenthesized, operator-composed reductionistic canonic gestalt (pocrcg) and - metaphysicalistic, demarcated, operator-composed reductionistic canonic gestalt (docrcg) The pncg consists of canonic formulas only and the number of formulas in a pncg depends on the length I being equal to the number of binary operators in a canonic formula of prcg. In a standard metaphysical case this number is always £ = n + 1 = 7. Thus, ^cang ■ a|=a a; Ca) H <£«) N ea) h Ca) H ^cc) 1= (ea H «); Ca) 1= (Ca N (e« N «)); (Ca 1= (Ca N (Ca N «))); ((«N3a)Nia) N (CaN (Ca N (<£a N (Ca N «)))); (a 1= J«) 1= (i, t= (e^a N (Ca H (