A World of Conceptual Graphs

Conceptual graphs (CGs) are a system of logic based on the existential graphs of Charles Sanders Peirce and the semantic networks of artificial intelligence. They express meaning in a form that is logically precise, humanly readable, and computationally tractable. With their direct mapping to language, conceptual graphs serve as an intermediate language for translating computer-oriented formalisms to and from natural languages. With their graphic representation, they serve as a readable, but formal design and specification language. CGs have been implemented in a variety of projects for information retrieval, database design, expert systems, and natural language processing.

Introductions to Conceptual Graphs

  • Simon Polovina and John Heaton, "An Introduction to Conceptual Graphs," AI Expert, pp. 36-43, 1992.

  • John F. Sowa, Information Processing in Mind and Machine. Reading, MA: Addison-Wesley Publ., 1984.

  • John F. Sowa, "Conceptual Graphs Summary," in Conceptual Structures: Current Research and Practice, P. Eklund, T. Nagle, J. Nagle, and L. Gerholz, eds., Ellis Horwood, 1992, pp. 3-52.

  • John Sowa's brief summary.

  • John Sowa, Knowledge Representation : Logical, Philosophical, and Computational Foundations, is not limited to conceptual graphs, but provides broad coverage of the entire field. It is available from Barnes and Noble books, Amazon.com etc.

  • Aalborg University's Department of Communication has developed an excellent Online Conceptual Graphs course

Conceptual Graphs Standard Notation

Current Proposal

There is a proposed standard, nearing its final stages, for the Conceptual Graphs Interchange Format (CGIF). This standard is being developed in conjunction with the ISO Common Logic Project, which seeks to standardize a form of logic for knowledge interchange, and includes three syntaxes for Common Logic, one of which is CGIF in Annex B. Comments and suggestions on the entire standard are welcome; see the web site for more details.

Old Proposals

Here are some older documents that may be of some historical interest. Note that CGIF has undergone significant changes from these documents; see the current proposal (above).

A very old draft proposed (c. 1998) for conceptual graphs:

Conceptual Graph Bibliographies

Bibliography from the CG standard

John Sowa's bibliography page

Conceptual Graphs Email List

An archive of the list messages (since September 2000) can be found at http://news.gmane.org/gmane.comp.ai.conceptual-graphs

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Research Groups and Projects

Universite Laval, Quebec City, Canada
Cognitive Informatics Laboratory

Virginia Polytechnic and State University (Virginia Tech)
Automatic Design Research Group

Washington State University
Conceptual Knowledge Markup Language Project
Ontology Links

University of California, Santa Cruz
Fast Conceptual Graph Retrieval and Question Answering

Development and use of CG tools
in knowledge base and expert systems, natural language processing, Case Based Reasoning and learning, Intelligent Tutoring Systems and Multi-Agent Systems.

Aalborg University - Department of Communication
Online Conceptual Graphs course


At ICCS'05 in Kassel, Germany, a discussion was held about how to further the progress of CG tools. Here is a summary of the discussion.

Amine, a multi-layer platform dedicated to the development of Intelligent Systems and Multi-agent Systems.

CharGer, a prototype conceptual graph editor developed the University of Alabama in Huntsville, free to noncommercial use, runs under Java

CPE - a modular environment that provides functional modules to give
functionality to a user without having to take the whole
environment. Currently, a CGIF and Basic CG Operations
(Projection and Maximal Join) are coming soon.

Notio - an API specification for a set of Java classes designed to provide an implementation-independent interface for manipulating Conceptual Graphs, GNU license

WebKB - tools for information retrieval and knowledge representation, availability??

CG Mars Lander - fast conceptual graph retrieval and question answering tool, available for joint development and industrial funding.

Prolog+CG - an object-oriented extension of PROLOG, based on CG. CG (both simple and compound) is a basic data structure, like term. PROLOG+CG is implemented with Java 2.

CoGITaNT - several useful utilities: a set of library routines in C++ for conceptual modeling, some knowledge bases in conceptual graphs, and an XML specification for CGXML. en francais.

See http://wiki.anykb.org/CG_tools for a comparison of many features of various CG tools.

There's also an older list of Conceptual Graph Tools

Individual Researchers