tailieunhanh - Báo cáo khoa học: "TEMPORAL CENTERING"

We present a semantic and pragmatic account of the anaphoric properties of past and perfect that improves on previous work by integrating discourse structure, aspectual type, surface structure and commonsense knowledge. A novel aspect of our account is that we distinguish between two kinds of temporal intervals in the interpretation of temporal operators - - discourse reference intervals and event intervals. This distinction makes it possible to develop an analogy between centering and temporal centering, which operates on discourse reference intervals. . | TEMPORAL CENTERING Megumi Kameyama SRI International Al Center 333 Ravenswood Ave. Menlo Park CA 94025 megumiQai. sri. com Rebecca Passonneau Dept of Computer Science Columbia University New York NY 10027 beckyQcs. Massimo Poesio Dept of Computer Science University of Rochester Rochester NY 14627-0226 poesio@ Abstract We present a semantic and pragmatic account of the anaphoric properties of past and perfect that improves on previous work by integrating discourse structure aspectual type surface structure and commonsense knowledge. A novel aspect of our account is that we distinguish between two kinds of temporal intervals in the interpretation of temporal operators discourse reference intervals and event intervals. This distinction makes it possible to develop an analogy between centering and temporal centering which operates on discourse reference intervals. Our temporal propertysharing principle is a defeasible inference rule on the logical form. Along with lexical and causal reasoning it plays a role in incrementally resolving underspecified aspects of the event structure representation of an utterance against the current context. The Problem The past tense has been compared with anaphoric definite pronouns 20 22 and definite noun phrases 27 . The supporting observation is that in two consecutive past tense descriptions of events as in 1 below from 18 the second sentence refers to a time t whose identity depends on the time t of the event described in the first sentence. l a. The Lone Ranger got on his horse t b. He rode off into the sunset t Tense interpretation also involves commonsense inferences in that the specific relation between the two event times may vary. In 1 the relation inferred to hold is temporal progression t - t but other ordering relations are also possible see 6 27 . Any temporal relations are in fact possible for two consecutively described events in discourse. A number of factors affect the interpretation as to