tailieunhanh - Báo cáo khoa học: "Some Properties of Preposition and Subordinate Conjunction Attachments*"

The present paper follows in the path set by these authors, but extends their work in significant ways. We made these extensions to solve this problem in a way that can be directly applied in running systems in such application areas as information extraction or conversational interfaces. In particular, we have sought to produce an attachment decision procedure with far broader coverage than in earlier approaches. Most research to date has focussed on a subset of the attachment problem that only covers 25% of the problem instances in our training data, the socalled binary VNP subset. Even the. | Some Properties of Preposition and Subordinate Conjunction Attachments Alexander s. Yeh and Marc B. Vilain MITRE Corporation 202 Burlington Road Bedford MA 01730 USA asy mbv @ phone 1-781-271-2658 Abstract Determining the attachments of prepositions and subordinate conjunctions is a key problem in parsing natural language. This paper presents a trainable approach to making these attachments through transformation sequences and error-driven learning. Our approach is broad coverage and accounts for roughly three times the attachment cases that have previously been handled by corpus-based techniques. In addition our approach is based on a simplified model of syntax that is more consistent with the practice in current state-of-the-art language processing systems. This paper sketches syntactic and algorithmic details and presents experimental results on data sets derived from the Penn Treebank. We obtain an attachment accuracy of for the general case the first such corpus-based result to be reported. For the restricted cases previously studied with corpusbased methods our approach yields an accuracy comparable to current work . 1 Introduction Determining the attachments of prepositions and subordinate conjunctions is an important problem in parsing natural language. It is also an old problem that continues to elude a complete solution. A classic example of the problem is the sentence I saw a man with a telescope where who had the telescope is ambiguous. Recently the preposition attachment problem has been addressed using corpus-based methods Hindle and Rooth 1993 Ratnaparkhi This paper reports on work performed at the MITRE Corporation under the support of the MITRE Sponsored Research Program. Useful advice was provided by Lynette Hirschman and David Palmer. The experiments made use of Morgan Pecelli s noun verb group annotations and some of David Day s programs. et al. 1994 Brill and Resnik 1994 Collins and Brooks 1995 Merlo et al. 1997 . The present