Processing and Representing Temporally Sequential Events

Processing and Representing Temporally Sequential Events Kiyong Lee Korea University 5ka-1 Anam-dong, Seongbuk-ku Seoul 136-701, Korea klee@korea.ac.kr Abstract In a discourse, events are narrated one by one linearly. But the temporal sequence of events does not always match the linear sequence of narration. One of such cases involves the mixed occurrences of durative and punctual events, as illustrated by “Mia took aspirin and slept, for she was ill. She then fell off a cliff in her dream." In this narration, five events are reported: three are durative events of sleeping, being ill and having a dream and two are punctual events of taking aspirin and falling off a cliff. This presentation aims at establishing some systematic way of processing such events and representing them in a reasonably understandable temporal sequence. For this, events are analyzed in terms of an interval semantics that allows them to be anchored to appropriate temporal intervals and be ordered in an appropriate temporal sequence. In order to provide a simple syntactic basis, the presentation attempts to develop a small computational program that derive representations in feature structure by analyzing a small fragment of Korean. 1 Introduction Events are often ordered in a temporal sequence and such sequential events are expressed in natural language either explicitly or implicitly. They are explicitly expressed by some subordinating conjuncts like “before" or “after" in English or by some unbound nouns like “cen-ey" (before) or “tawum-ey" (after) in Korean. But they may also be expressed in coordinate structures by the sequential occurrences of verbs. Here is a simple example in English, “Mia went to Tokyo, met a friend and stayed at her home." This sentence narrates three sequential events of Mia’s going to Tokyo, meeting a friend and staying at the friend’s home. The sequence of narration, however, does not always match that of events. One such case involves the mixed occurrences of durative events and punctual events. Consider a case “Mia was ill and took pills and took a nap. She then had a bad dream. She fell off a cliff." This sentence narrates five events, three durative events of being ill, taking a nap, and having a bad dream and two punctual events of taking pills and falling off a cliff. This paper aims at showing how such events can be processed and represented for the proper interpre- tation of their temporal sequences. For this aim, I make two basic assumptions: one is a minimal syntax as argued for in Lee (2002) and another, a minimal semantic representation that will be shown in this work. 2 Two Types of Temporal Relations There are at least two types of temporal relations over events: precedence and inclusion. The past tense is a typical example of temporal precedence. An event described by a statement made with an utterance “Mia slept" is understood as preceding the event of making such an utterance, thus being an event in PACLIC 18, December 8th-10th, 2004, Waseda University, Tokyo - 9 - the past. Another example …

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