An Empirical Approach to Temporal Reference Resolution

An Empirical Approach to Temporal Reference Resolution Janyce Wiebe, Tom O'Hara, Kenneth McKeever, and Thorsten OhrstrSm-Sandgren Dept. of Computer Science and the Computing Research Laboratory New Mexico State University Las Cruces, NM 88003 wiebe, t omohara, kmckeeve, t s andgre@c s. nmsu. edu Abstract This paper presents the results of an em- pirical investigation of temporal reference resolution in scheduling dialogs. The algo- rithm adopted is primarily a linear-recency based approach that does not include a model of global focus. A fully automatic system has been developed and evaluated on unseen test data with good results. This paper presents the results of an intercoder reliability study, a model of temporal refer- ence resolution that supports linear recency and has very good coverage, the results of the system evaluated on unseen test data, and a detailed analysis of the dialogs as- sessing the viability of the approach. 1 Introduction Temporal information is often a significant part of the meaning communicated in dialogs and texts, but is often left implicit, to be recovered by the listener or reader from the surrounding context. Determin- ing all of the temporal information that is being conveyed can be important for many interpretation tasks. For instance, in machine translation, know- ing the temporal context is important in translating sentences with missing information. This is partic- ularly useful when dealing with noisy data, as with spoken input (Levin et al. 1995). In the following example, the third utterance could be interpreted in three different ways. sl: (Ahora son las once y diez) Now it is eleven ten sl: (Qu4 tal a las doce) How about twelve sl: (Doce ados) Twelve to two or The twelfth to the second or The twelfth at two By maintaining the temporal context (i.e., the 5th of March 1993 at 12:00), the system will know that "12:00 to 2:00" is a more probable interpretation than "the 12th at 2:00". In addition, maintaining the temporal context would be useful for information extraction tasks dealing with natural language texts such as memos or meeting notes. For instance, it can be used to resolve relative time expressions, so that absolute dates can be entered in a database with a uniform representation. This paper presents the results of an empiri- cal investigation of temporal reference resolution in scheduling dialogs (i.e., dialogs in which participants schedule a meeting with one another). This work thus describes how to identify temporal information that is missing due to ellipsis or anaphora, and it shows how to determine the times evoked by deictic expressions. In developing the algorithm, our ap- proach was to start with a straightforward, recency- based approach and add complexity as needed to address problems encountered in the data. The al- gorithm does not include a mechanism for handling global focus (Grosz & Sidner 1986), for centering within a discourse segment (Sidner 1979; Grosz et al. 1995), or for performing tense and aspect interpreta- tion. Instead, the algorithm processes anaphoric ref- erences with respect to an Attentional State …

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