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Cyc

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For the theatrical and photographic backdrop, see Cyclorama (theater).

Cyc is an artificial intelligence project that attempts to assemble a comprehensive ontology and database of everyday common sense knowledge, with the goal of enabling AI applications to perform human-like reasoning.

Overview

The project was started in 1984 by Doug Lenat as part of Microelectronics and Computer Technology Corporation. The name "Cyc" (from "encyclopedia", pronounced like psych) is a registered trademark owned by Cycorp, Inc. in Austin, Texas, a company run by Lenat and devoted to the development of Cyc. The original knowledge base is proprietary, but a smaller version of the knowledge base, intended to establish a common vocabulary for automatic reasoning, was released as OpenCyc under an open source license. More recently, Cyc has been made available to AI researchers under a research-purposes license as ResearchCyc.

Typical pieces of knowledge represented in the database are "Every tree is a plant" and "Plants die eventually". When asked whether trees die, the inference engine can draw the obvious conclusion and answer the question correctly. The Knowledge Base (KB) contains over a million human-defined assertions, rules or common sense ideas. These are formulated in the language CycL, which is based on predicate calculus and has a syntax similar to that of the Lisp programming language. CycL users pun that they are "cyclists".

Much of the current work on the Cyc project continues to be knowledge engineering, representing facts about the world by hand, and implementing efficient inference mechanisms on that knowledge. Increasingly, however, work at Cycorp involves giving the Cyc system the ability to communicate with end users in natural language, and to assist with the knowledge formation process via machine learning.

Description of the Knowledge Base, terminology

The concept names in Cyc are known as constants. Constants start with an optional "#$" and are case-sensitive. There are constants for:

  • Individual items known as individuals, such as #$BillClinton or #$France.
  • Collections, such as #$Tree-ThePlant (containing all trees) or #$EquivalenceRelation (containing all equivalence relations). A member of a collection is called an instance of that collection.
  • Truth Functions which can be applied to one or more other concepts and return either true or false. For example #$siblings is the sibling relationship, true if the two arguments are siblings. By convention, truth function constants start with a lower-case letter. Truth functions may be broken down into logical connectives (such as #$and, #$or, #$not, #$implies), quantifiers (#$forAll, #$thereExists, etc.) and predicates.
  • Functions, which produce new terms from given ones. For example, #$FruitFn, when provided with an argument describing a type (or collection) of plants, will return the collection of its fruits. By convention, function constants start with an upper-case letter and end with the string "Fn".

The most important predicates are #$isa and #$genls. The first one describes that one item is an instance of some collection, the second one that one collection is a subcollection of another one. Facts about concepts are asserted using certain CycL sentences. Predicates are written before their arguments, in parentheses: 

 (#$isa #$BillClinton #$UnitedStatesPresident)

"Bill Clinton belongs to the collection of U.S. presidents" and 

 (#$genls #$Tree-ThePlant #$Plant)

"All trees are plants". 

 (#$capitalCity #$France #$Paris)

"Paris is the capital of France."

Sentences can also contain variables, strings starting with "?". These sentences are called "rules". One important rule asserted about the #$isa predicate reads 

(#$implies
   (#$and   
     (#$isa ?OBJ ?SUBSET)
     (#$genls ?SUBSET ?SUPERSET))
   (#$isa ?OBJ ?SUPERSET))

with the interpretation "if OBJ is an instance of the collection SUBSET and SUBSET is a subcollection of SUPERSET, then OBJ is an instance of the collection SUPERSET". Another typical example is 

 (#$relationAllExists #$biologicalMother #$ChordataPhylum #$FemaleAnimal)

which means that for every instance of the collection #$ChordataPhylum (i.e. for every chordate), there exists a female animal (instance of #$FemaleAnimal) which is its mother (described by the predicate #$biologicalMother).

The knowledge base is divided into microtheories (Mt), collections of concepts and facts typically pertaining to one particular realm of knowledge. Unlike the knowledge base as a whole, each microtheory is required to be free from contradictions. Each microtheory has a name which is a regular constant; microtheory constants contain the string "Mt" by convention. An example is #$MathMt, the microtheory containing mathematical knowledge. The microtheories can inherit from each other and are organized in a hierarchy: one specialization of #$MathMt is #$GeometryGMt, the microtheory about geometry.

OpenCyc

The latest version of OpenCyc, 1.0, was released in July 2006. OpenCyc 1.0 includes the entire Cyc ontology containing hundreds of thousands of terms, along with millions of assertions relating the terms to each other. The knowledge base contains 47,000 concepts and 306,000 facts and can be browsed on the OpenCyc website. The first version of OpenCyc was released in May 2001 and contained only 6,000 concepts and 60,000 facts. The knowledge base is released under the Apache License. Cycorp has stated its intention to release OpenCyc under parallel, unrestricted licences to meet the needs of its users. The CycL and SubL interpreter (the program that allows you to browse and edit the database as well as to draw inferences) is released free of charge, but only as a binary, without source code. It is available for GNU/Linux and for Windows.

ResearchCyc

In July 2006, Cycorp released ResearchCyc 1.0, a free (but not open source) version of Cyc aimed at the research community. (ResearchCyc was in beta stage of development during all of 2004; a beta version was released in February 2005.) In addition to the taxonomic information contained in OpenCyc, ResearchCyc includes significantly more semantic knowledge (i.e., additional facts) about the concepts in its knowledge base, and includes a large lexicon, English parsing and generation tools, and Java based interfaces for knowledge editing and querying.

Cycorp has publicly stated its intention of releasing all of the terms and taxonomic relationships contained in ResearchCyc as part of OpenCyc and this will supposedly be achieved with a future release of OpenCyc. One stated goal is that of providing a completely free and unrestricted semantic vocabulary for use in the Semantic Web. The OpenCyc taxonomy supposedly will become available in Owl on the OpenCyc web site.

Criticisms of the Cyc Project

The Cyc project has been described as "one of the most controversial endeavours of the artificial intelligence history" (Bertino et al, p. 275), so it has inevitably garnered its share of criticism. Criticisms include:

  • The complexity of the system - arguably necessitated by its encyclopædic ambitions - and the consequent difficulty in adding to the system by hand
  • Scalability problems from widespread reification, especially as constants
  • Unsatisfactory treatment of the concept of substance and the related distinction between intrinsic and extrinsic properties
  • The lack of any meaningful benchmark or comparison for the efficiency of Cyc's inference engine
  • The current incompleteness of the system in both breadth and depth and the related difficulty in measuring its completeness
  • Limited documentation
  • The lack of up-to-date on-line training material makes it difficult for new people to learn the systems
  • A large number of gaps in not only the ontology of ordinary objects but an almost complete lack of relevant assertions describing such objects

See also

References

  • Elisa Bertino, Gian Piero Zarri, Barbara Catania, Gian Pierro Zarri (2001). Intelligent Database Systems. Addison-Wesley Professional. ISBN ISBN 0-201-87736-8.{{cite book}}: CS1 maint: multiple names: authors list (link)
  • Matuszek, Cynthia, M. Witbrock, R. Kahlert, J. Cabral, D. Schneider, P. Shah and D. Lenat. Searching for Common Sense: Populating Cyc from the Web. In Proceedings of the Twentieth National Conference on Artificial Intelligence, Pittsburgh, Pennsylvania, July 2005.[1]
  • Shepard, Blake, C. Matuszek, C.B. Fraser, W. Wechtenhiser, D. Crabbe, Z. Güngördü, J. Jantos, T. Hughes, L. Lefkowitz, M. Witbrock, D. Lenat, E. Larson. A Knowledge-Based Approach to Network Security: Applying Cyc in the Domain of Network Risk Assessment. In Proceedings of the Seventeenth Innovative Applications of Artificial Intelligence Conference, Pittsburgh, Pennsylvania, July 2005.[2]
  • Ramachandran, Deepak, P. Reagan, K. Goolsbey. First-Orderized ResearchCyc: Expressivity and Efficiency in a Common-Sense Ontology. In Papers from the AAAI Workshop on Contexts and Ontologies: Theory, Practice and Applications. Pittsburgh, Pennsylvania, July 2005.[3]
  • Cabral, John, R.C. Kahlert, C. Matuszek, M. Witbrock, B. Summers. Converting Semantic Meta-Knowledge into Inductive Bias. In Proceedings of the 15th International Conference on Inductive Logic Programming, Bonn, Germany, August 2005.[4]
  • Schneider, Dave, C. Matuszek, P. Shah, R. Kahlert, D. Baxter, J. Cabral, M. Witbrock, D. Lenat. Gathering and Managing Facts for Intelligence Analysis. In Proceedings of the 2005 International Conference on Intelligence Analysis, McLean, Virginia, May 2005.[5]
  • Forbus, Kenneth, L. Birnbaum, E. Wagner, J. Baker & M. Witbrock. Combining analogy, intelligent information retrieval, and knowledge integration for analysis: A preliminary report. In Proceedings of the 2005 International Conference on Intelligence Analysis, McLean, Virginia, May 2005.[6]
  • Deaton, Chris, B. Shepard, C. Klein, C. Mayans, B. Summers, A. Brusseau, M. Witbrock. The Comprehensive Terrorism Knowledge Base in Cyc. In Proceedings of the 2005 International Conference on Intelligence Analysis, McLean, Virginia, May 2005.[7]
  • Rode, Benjamin. Towards a Model of Pattern Recovery in Relational Data. In Proceedings of the 2005 International Conference on Intelligence Analysis, McLean, Virginia, May 2005.[8]
  • Siegel, Nick, B. Shepard, J. Cabral, M. Witbrock. Hypothesis Generation and Evidence Assembly for Intelligence Analysis: Cycorp's Nooscape Application. In Proceedings of the 2005 International Conference on Intelligence Analysis, McLean, Virginia, May 2005.[9]
  • Curtis, Jon, G. Matthews, D. Baxter. On the Effective Use of Cyc in a Question Answering System in Papers from the IJCAI Workshop on Knowledge and Reasoning for Answering Questions, Edinburgh, Scotland: 2005.[10]
  • Witbrock, Michael, C. Matuszek, A. Brusseau, R.C. Kahlert, C.B. Fraser, D. Lenat. Knowledge Begets Knowledge: Steps towards Assisted Knowledge Acquisition in Cyc in Papers from the 2005 AAAI Spring Symposium on Knowledge Collection from Volunteer Contributors (KCVC), pp. 99-105. Stanford, California, March 2005.[11]
  • Belasco, Alan, J. Curtis, RC Kahlert, C. Klein, C. Mayans, R. Reagan. Representing Knowledge Gaps Effectively. In D. Karagiannis, U. Reimer (Eds.): Practical Aspects of Knowledge Management, Proceedings of PAKM 2004, Vienna, Austria, December 2-3, 2004, Springer-Verlag, Berlin Heidelberg.[12]
  • Siegel, Nick, G. Matthews, J. Masters, R. Kahlert, M. Witbrock and K. Pittman. Agent Architectures: Combining the Strengths of Software Engineering and Cognitive Systems in Papers from the AAAI Workshop on Intelligent Agent Architectures: Combining the Strengths of Software Engineering and Cognitive Systems, Technical Report WS-04-07, pp. 74-79. Menlo Park, California: AAAI Press, 2004.[13]
  • Witbrock, Michael, K. Panton, S.L. Reed, D. Schneider, B. Aldag, M. Reimers and S. Bertolo. Automated OWL Annotation Assisted by a Large Knowledge Base in Workshop Notes of the 2004 Workshop on Knowledge Markup and Semantic Annotation at the 3rd International Semantic Web Conference ISWC2004, Hiroshima, Japan, November 2004, pp. 71-80.[14]
  • Masters, James and Z. Güngördü. Structured Knowledge Source Integration: A Progress Report. In Integration of Knowledge Intensive Multiagent Systems, Cambridge, Massachusetts, USA, 2003.[15]
  • O'Hara, Tom, N. Salay, M. Witbrock, et al. Inducing criteria for mass noun lexical mappings using the Cyc Knowledge Base and its Extension to WordNet. In Proceedings of the Fifth International Workshop on Computational Semantics, Tilburg, 2003.[16]
  • Witbrock, Michael, D. Baxter, J. Curtis, et al. An Interactive Dialogue System for Knowledge Acquisition in Cyc. In Proceedings of the Eighteenth International Joint Conference on Artificial Intelligence, Acapulco, Mexico, 2003.[17]
  • Panton, Kathy, P. Miraglia, N. Salay, et al. Knowledge Formation and Dialogue Using the KRAKEN Toolset. In Eighteenth National Conference on Artificial Intelligence, Edmonton, Canada, 2002.[18]
  • Masters, James. Structured Knowledge Source Integration and its applications to information fusion. In Proceedings of the Fifth International Conference on Information Fusion, Annapolis, MD, July 2002.[19]
  • Reed, Stephen and D. Lenat. Mapping Ontologies into Cyc. In AAAI 2002 Conference Workshop on Ontologies For The Semantic Web, Edmonton, Canada, July 2002.[20]
  • D. Lenat and R. V. Guha. (1990). Building Large Knowledge-Based Systems: Representation and Inference in the Cyc Project. Addison-Wesley. ISBN 0-201-51752-3.
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