Compréhension de Textes dans un domaine technique :le système ACTES.Application des Grammaires d'Unification et de la Théorie du Discours

Automatic processing of specification texts written in natural language raises at least two problems: the availability of general tools to recognize the constituents of the texts; finding a way to represent their contents allowing the user to modify and check them for consistency. The texts analyzed here specified the alarm logic for an aircraft. The long-term aim is to extract rules for an expert system simulating the behavior of the airborne processors responsible for managing the alarms. The ACTES system offers, on the one hand, a formalism allowing grammars to be defined and an intermediate semantic representation of the texts to be made, and , on the other hand, an environment for the development of grammars and for texts analysis. The formalism is inspired from unification-based grammars and the Discourse Representation Theory. The approach implemented has the advantage of being unified: the syntax and the semantics are processed by the PROLOG unification operation. But since Prolog does not take into account hierarchical mecanisms, we defined an extended unification operation which manages hierarchical constraints among the typed elements of the formalism. The environment includes, among others, an anaphora resolver which integrates multiple constraint sources which have their own strategies in a blackboard architecture. As regards the final representation model of the content of a text, it is inspired from the Default Logic. This logic satisfactorily reflects the non-monotonic construction of these texts. It allows interactive modification with consistency checks to be envisaged.