Event-building through Role-filling and Anaphora Resolution

Event-building through Role-filling and Anaphora Resolution Greg Whittemore Electronic Data Systems Corp. 5951 Jefferson Street N.E. Albuquerque, NM 87109-3432 greg@edsr.eds.com Melissa Macpherson Electronic Data Systems Corp. 5951 Jefferson Street N.E. Albuquerque, NM 87109-3432 melissa@edsr.eds.eom Greg Carlson Linguistics Program, University of Rochester Rochester, NY grca~uorvm.bitnet ABSTRACT In this study we map out a way to build event representations incrementally, using information which may be widely distributed across a dis- course. An enhanced Discourse Representation (Kamp, 1981) provides the vehicle both for car- rying open event roles through the discourse until they can be instantiated by NPs, and for resolving the reference of these otherwise problematic NPs by binding them to the event roles. INTRODUCTION The computational linguistics literature includes a wide variety of ideas about how to represent events in as much detail as is required for reason- ing about their implications. Less has been writ- ten about how to use information in text to incre- mentally build those event representations as dis- course progresses, especially when the identifica- tion of event participants and other details is dis- persed across a number of structures. We will be concerned here with providing a representational framework for this incremental event-building, and with using that representation to examine the ways in which reference to the internal structure of events contributes to discourse cohesion. That is, we will be interested both in the process of gleaning fully-specified event descriptions from continuous text, and in showing how individual elements of an event's internal structure can behave anaphorically. Examples of the kinds of linkages that must be dealt with in building representations of events from text follow: la) He was believed Co be a liar. b) We promised him to be truthful. c) He tried to keep his mouth shut. 2a) Joe gave Pete a book to read. b) Joe gave Pete a book to impress him. c) Joe asked Pete for a book to read. d) I asked Joe for a book to impress Sam. e) Joe gave Pete the message to save his skin. 3a) Joe told Pete that to err is human. b) He told us that to quit eould be silly. 4a) GM will broaden collaboration with Lotus to make a new car. b) Mary thought that an argument with herself would be entertaining. c) Mary thought that a conference with himself would make John look silly. The examples in (1) are familiar cases of syntac- tically obligatory control; we will consider their be- havior to be straightforwardly and locally resolved. The sentences of (2) show infinitival relatives, pur- pose, and 'in-order-to' clauses in which control of the infinitive (and hence of its implicit subject) is sometimes clear, sometimes ambiguous. In (3), a subject infinitival phrase receives an unavoidably generic reading in one case and a non-generic but ambiguous reading in the other. Finally, the exam- ples of (4) indicate that nominalizations of events also have roles whose reference must be determined, and whose existence and identity has consequences for subsequent discourse. Aside …

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