The Classic Family of Knowledge Representation Systems

Classic is a family of knowledge representation (KR) systems designed for applications where only limited expressive power is necessary, but rapid responses to questions are essential. The Classic systems are based on description logics (DLs), which gives them an object-centered flavor, and thus most of the features available in semantic networks are also available in Classic. Classic has a framework that allows users to represent descriptions, concepts, roles, individuals and rules. Classic allows for both primitive concepts, similar to the classes and frames of other knowledge representation systems and object-oriented programming languages, and defined concepts, i.e. concepts that have both necessary and sufficient conditions for membership. Concepts are automatically organized into a generalization taxonomy and objects are automatically made instances of all concepts for which they pass the membership test. Another type of reasoning that Classic does is to detect inconsistencies in information that it is told. In the presence of defined concepts these operations are non-trivial and useful.

There are other implemented description logics besides the Classic systems. Some other implemented systems are mentioned on this site, or for more complete information about description logics, see the official description logic home page.

There are three members of the Classic family. They are:

the LISP version,
which is the original version that was developed for research purposes,
the C version,
which was written for configuration applications and is also called C-Classic,
and NeoClassic,
which is the newest version and is written in C++.

Classic has been distributed to over 100 research institutions. The C version is a vital component of the PROSE and QUESTAR configuration products which have been used to configure over 4 billion dollars worth of AT&T and Lucent products. A demonstration application on configuring home theater systems has been developed in LISP Classic. A new web version of the configuration system is sometimes available.

Online tutorials (co-developed with Rich Thomason, Violetta Cavalli-Sforza, Cristina Conati, and Johanna Moore from University of Pittsburgh) are available for the LISP version as well as the NeoClassic version. The LISP tutorial was distributed from the University of Pittsburgh and may be available on from ~ftp/pub/classic-tutorial. Rich Thomason is the Pitt contact for the tutorial. Both tutorials (LISP and NeoClassic) are available from these pages.

Related research activities in description logics include explaining inferences in description logic systems, pruning object presentation, extensible description logics, default representation, machine learning applied to description logics, etc.

Obtaining Classic

LISP Classic and NeoClassic are available for non-commercial use They are also available for commercial use, though this requires previous negotiation of terms and conditions. You should be able to obtain a copy of LISP Classic or NeoClassic, but the distribution mechanism is currently broken. To obtain a copy of LISP Classic or NeoClassic, go to the Bell Labs open innovation site, The page for Classic, including NeoClassic, is

People who have worked on the Classic Projects

Selected References

  • Deborah L. McGuinness and Peter F. Patel-Schneider. ``Usability Issues in Knowledge Representation Systems,'' in Proceedings of the Fifteenth National Conference on Artificial Intelligence, Madison, Wisconsin, 1998. abstract
  • Ronald J. Brachman, Deborah L. McGuinness, Peter F. Patel-Schneider, Lori Alperin Resnick, and Alex Borgida, `` Living with CLASSIC: When and How to Use a KL-ONE-Like Language,'' in John Sowa, ed., Principles of Semantic Networks: Explorations in the representation of knowledge , Morgan-Kaufmann: San Mateo, California, 1991, pages 401--456.
  • Alex Borgida, Ronald J. Brachman, Deborah L. McGuinness, and Lori Alperin Resnick, ``CLASSIC: A Structural Data Model for Objects,'' in Proceedings of the 1989 ACM SIGMOD International Conference on Management of Data , pages 59--67, June 1989.
  • Deborah L. McGuinness and Jon R. Wright. ``An Industrial Strength Description Logic-based Configurator Platform.'' IEEE Intelligent Systems, Vol. 13, No. 4, July/August 1998, pp. 69-77. abstract
  • Deborah L. McGuinness and Jon R. Wright. ``Conceptual Modeling for Configuration: A Description Logic-based Approach,'' to appear in Artificial Intelligence for Engineering Design, Analysis and Manufacturing Journal, Special Issue on Configuration, 1998. abstract
  • J. R. Wright, E. S. Weixelbaum, K. Brown, G. T. Vesonder, S. R. Palmer, J. I. Berman, and H. H. Moore, ``A knowledge-based configurator that supports sales, engineering, and manufacturing at AT&T network systems,'' in Proceedings of the Innovative Applications of Artificial Intelligence Conference, pp.183--193, 1993.
  • R. J. Brachman, P. G. Selfridge, L. G. Terveen, B. Altman, A. Borgida, F. Halper, T. Kirk, A. Lazar., D. L. McGuinness, and L. A. Resnick, ``Integrated Support for Data Archaeology,'' in International Journal of Intelligent and Cooperative Information Systems , 2:159-185, 1993.
  • Alon Y. Levy, Anand Rajaraman and Joann J. Ordille, ``Query Answering Algorithms for Information Agents'' Proceedings of the 13th National Conference on Artificial Intelligence, AAAI-96, Portland, Oregon, August, 1996. abstract
  • Thomas Kirk, Alon Y. Levy, Yehoshua Sagiv, and Divesh Srivastava, ``The Information Manifold'', Working Notes of the AAAI Spring Symposium on Information Gathering from Heterogeneous Distributed Environments, 1995.
  • For more information write to Peter F. Patel-Schneider (

    Updated 21 August 2008 by Peter F. Patel-Schneider