tailieunhanh - Báo cáo khoa học: "Using Document Level Cross-Event Inference to Improve Event Extraction"

Event extraction is a particularly challenging type of information extraction (IE). Most current event extraction systems rely on local information at the phrase or sentence level. However, this local context may be insufficient to resolve ambiguities in identifying particular types of events; information from a wider scope can serve to resolve some of these ambiguities. In this paper, we use document level information to improve the performance of ACE event extraction. | Using Document Level Cross-Event Inference to Improve Event Extraction Shasha Liao New York University 715 Broadway 7th floor New York NY 10003 USA liaoss@ Ralph Grishman New York University 715 Broadway 7th floor New York NY 10003 USA grishman@ Abstract Event extraction is a particularly challenging type of information extraction IE . Most current event extraction systems rely on local information at the phrase or sentence level. However this local context may be insufficient to resolve ambiguities in identifying particular types of events information from a wider scope can serve to resolve some of these ambiguities. In this paper we use document level information to improve the performance of ACE event extraction. In contrast to previous work we do not limit ourselves to information about events of the same type but rather use information about other types of events to make predictions or resolve ambiguities regarding a given event. We learn such relationships from the training corpus and use them to help predict the occurrence of events and event arguments in a text. Experiments show that we can get absolute gain in trigger event classification and more than 8 gain for argument role classification in ACE event extraction. 1 Introduction The goal of event extraction is to identify instances of a class of events in text. The ACE 2005 event extraction task involved a set of 33 generic event types and subtypes appearing frequently in the news. In addition to identifying the event itself it also identifies all of the participants and attributes of each event these are the entities that are involved in that event. Identifying an event and its participants and attributes is quite difficult because a larger field of view is often needed to understand how facts tie together. Sometimes it is difficult even for people to classify events from isolated sentences. From the sentence 1 He left the company. it is hard to tell whether it is a Transport .