Computational aspects of discourse in the context of MUC-3

Discourse comprises those phenomena that usually do not arise when processing a single sentence. It appears to be the most difficult and probably the least understood aspect of automated message understanding. Five out of fifteen sites on a MUC-3 survey listed discourse as their main weakness and an area in which to concentrate future research. Virtually all systems presented here take a sentence-by-sentence approach to text understanding. Parsing and domain-dependent interpretation of sentences or sentence fragments (usually the latter) are followed by modules that attempt to connect these interpretations into a coherent whole. This paper gives an overview of the modules that make the transition from the interpretation of sentences to the interpretation of the text that contains these sentences. Systems presented in this paper exhibit various degrees of the following discourse understanding capabilities:• identifying portions of text that describe different domain events; this includes the capability of recognizing a single event and the capability of distinguishing multiple events;• resolving references:- pronoun references, e.g., finding the referent of It in the sentence It took place this morning,- proper name references, e.g., understanding that Luis Galan may be referred to as Senator Galan;- definite references, e.g., deciding what is the referent for The attack in the sentence The attack look us by surprise.• discourse representation : representation at the message level.