The classical CHAT80 natural language system

The CHAT80 system has been developed in the 70s and 80s by Fernando C.N. Pereira and David H.D. Warren. It implements a natural language question answering system that answers questions about the world: countries, cities, rivers, etc. It does so by parsing the question, translate the parse to a Prolog query and run this against its database.

This version is derived from the original via Quintus Prolog after some compatibility modifications for SWI-Prolog and adding a module header that allows using it safely together with other applications.

The code is definitely dated. Still, it provides a nice example using Prolog for parsing, assigning meaning and querying.

Legal

On August 10 2020, the code was re-licensed on request from the original authors David H. D. Warren and Fernando C. N. Pereira on request from Vijay Saraswat. CHAT-80 is now available under the MIT license.