Extending the Expressive Capacity of the Semantic Component of the OPERA System

OPERA is a natural language question answering system allowing the interrogation of a data base consisting of an extensive listing of operas. The linguistic front-end of OPERA is a comprehensive grammar of French, and its semantic component translates the syntactic analysis into logical formulas (first order logic formulas).However there are quite a fiew constructions which can be analysed syntactically in the grammar but for which we are unable to specify translations. Foremost among these are anaphoric and elliptic contructions. Thus this paper describes the extension of OPERA to anaphoric and elliptic constructions on the basis of the Discourse Representation Theory (DRT).