Event-Building through Role-Filling and Anaphora Resolution

In this study we map out a way to build event representations incrementally, using information which may be widely distributed across a discourse. An enhanced Discourse Representation (Kamp, 1981) provides the vehicle both for carrying 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. I N T R O D U C T I O N The computational linguistics literature includes a wide variety of ideas about how to represent events in as much detail as is required for reasoning about their implications. Less has been written about how to use information in text to incrementally build those event representations as discourse progresses, especially when the identification of event participants and other details is dispersed 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 t r i e d t o k e e p h i s mouth s h u t . 2a) Joe gave P e t e a book t o r e a d . b) Joe gave P e t e a book t o i m p r e s s him. c ) Joe a s k e d P e t e f o r a book t o r e a d . d) I a s k e d Joe f o r a book t o i m p r e s s Sam. e) Joe gave P e t e t h e m e s s a g e t o s a v e h i s s k i n . 3a) Joe t o l d P e t e t h a t t o e r r i s human. b) He t o l d us t h a t t o q u i t e o u l d be s i l l y . 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 syntactically obligatory control; we will consider their behavior to be straightforwardly and locally resolved. The sentences of (2) show infinitival relatives, purpose, 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 examples 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 from the sentences in (1), in which control is unambiguously sorted out within the sentence on the basis of verb type, all the examples above can