Showing papers by "Nicholas Asher published in 1988"

A computational account of syntactic, semantic and discourse principles for anaphora resolution

Abstract: We present a unified framework for the computational implementation of syntactic, semantic, pragmatic and even \"stylistic\" constraints on anaphora. We build on our BUILDRS implementation of Discourse Representation (DR) Theory and Lexical Functional Grammar (LFG) discussed in Wada & Asher (1986). We develop and argue for a semantically based processing model for anaphora resolution that exploits a number of desirable features: (1) the partial semantics provided by the discourse representation structures (DRSs) of DR theory, (2) the use of syntactic and lexical features to filter out unacceptable potential anaphoric antecedents from the set of logically possible antecedents determined by the logical structure of the DRS, (3) the use of pragmatic or discourse constraints, noted by those working on focus, to impose a salience ordering on the set of grammatically acceptable potential antecedents. Only where there is a marked difference in the degree of salience among the possible antecedents does the salience ranking allow us to make predictions on preferred readings. In cases where the difference is extreme, we predict the discourse to be infelicitous if, because of other constraints, one of the markedly less salient antecedents must be linked with the pronoun. We also briefly consider the applications of our processing model to other definite noun phrases besides anaphoric pronouns.

Reasoning about belief and knowledge with self-reference and time

Abstract: In two previous papers (Asher & Kamp 1986,1987), Hans Kamp and I developed a framework for investigating the logic of attitudes whose objects involved an unlimited capacity for self-reference. The framework was the daughter of two well-known parents-- possible worlds semantics and the revisionist, semi-inductive theory of truth developed by Herzberger (1982) and Gupta (1982). Nevertheless, the offspring from our point of view was not an entirely happy one. We had argued that orthodox possible worlds semantics was an unacceptable solution to the problem of the semantics of the attitudes. Yet the connection between our use of possible worlds semantics and the sort of representational theories of the attitudes that we favor remained unclear. This paper attempts to provide a better connection between the framework developed in the previous papers and representational theories of attitudes by developing a notion of reasoning about knowledge and belief that a careful examination of the model theory suggests. This notion of reasoning has a temporal or dynamic aspect that I exploit by introducing temporal as well as attitudinal predicates.