The Interpretation of Tense in Discourse

THE INTERPRETATION OF TENSE IN DISCOURSE Bonnie Lynn Webber Department of Computer & Information Science University of Pennsylvania Philadelphia PA 19104-6389 Abstract This paper gives an account of the role tense plays in the listener's reconstruction of the events and situations a speaker has chosen to describe. Several new ideas are presented: (a) that tense is better viewed by analogy with definite NPs than with pronouns; (b) that a narrative has a temporal focus that grounds the context-dependency of tense; and (c) that focus management heuristics can be used to track the movement of temporal focus. 1 1. Introduction My basic premise is that in processing a narrative text, a listener is building up a representation of the speaker's view of the events and situations being described and of their relationship to one another. This representation, which I will call an eventJsituatlon structure or e/s structure, reflects the listener's best effort at interpreting the speaker's ordering of those events and situations in time and space. The listener's problem can therefore be viewed as that of establishing where in the evolving els structure to attach the event or situation described in the next clause. My claim is that the discourse interpretation of tense contributes to the solution of this problem. This work on the discourse interpretation of tense is being carried out in the context of a larger enterprise whose goal is an account of explicit anaphoric reference to events and situations, as in Example 1. Example 1 It's always been presumed that when the glaciers receded, the area got very hot. The Folsum men couldn't adapt, and they died out. That's what's supposed to have happened./t's the textbook dogma. But it's wrong. They were human and smart. They adapted their weapons and culture, and they survived. Example 1 shows that one may refer anaphorically to structured entities built up through multiple clauses. Thus an account of how clauses arrange themselves into structures is necessary to an account of event reference. 2 IThis work was papally supported by ARO grant DAA29-84og-0027, NSF grant MCS-8219116-CER, and DARPA grant N00014-85-K-0018 to the University of Pennsylvania, and by DARPA grant N00014-aS.-C-0012 to UNISYS. =Other parts of ~e entemrise include a ganeraJ mechanism for individuating composite entities made up of ones separately introduced I20, 21J and a representation for events that aJlow for anaphoric reference to both particular events and situations and to abstractions thereof [16], In this paper, I will relate the problem of building up an e/s structure to what has been described as the anaphoric property of tense [7, 11, 6, 1, 12] and of relative temporal adverbials[18]. Anaphora are expressions whose specification is context-dependent. Tense and relative temporal adverbials, I interpret as specifying positions in an evolving els structure. My view of their anaphoric nature is that the particular positions they can specify depend on the current context. And the current context only makes a few positions accessible. (This I will claim to be in contrast with the ability of temporal …

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