Lexical Disambiguation in a Discourse Context

In this paper we investigate how discourse structure a ects the meanings of words and how the meanings of words a ect discourse structure We integrate three ingredients a theory of discourse structure called sdrt which represents discourse in terms of rhetorical relations that glue together the propositions introduced by the text segments an accom panying theory of discourse attachment called dice which computes which rhetorical relations hold between the constituents on the basis of the reader s background infor mation and a formal language for specifying the lexical knowledge both syntactic and semantic called the lkb Through this integration we can model the information ow from words to discourse and discourse to words From words to discourse we show how the lkb permits the rules for computing rhetorical relations in dice to be generalised and simpli ed so that a single law applies to several semantically related lexical items From discourse to words we encode two novel heuristics for lexical disambiguation dis ambiguate words so that discourse incoherence is avoided and disambiguate words so that rhetorical connections are reinforced These heuristics enable us to tackle several cases of lexical disambiguation that have until now been outside the scope of theories of lexical processing