tailieunhanh - Báo cáo khoa học: "Using Syntax to Disambiguate Explicit Discourse Connectives in Text"

Discourse connectives are words or phrases such as once, since, and on the contrary that explicitly signal the presence of a discourse relation. There are two types of ambiguity that need to be resolved during discourse processing. First, a word can be ambiguous between discourse or non-discourse usage. For example, once can be either a temporal discourse connective or a simply a word meaning “formerly”. Secondly, some connectives are ambiguous in terms of the relation they mark. | Using Syntax to Disambiguate Explicit Discourse Connectives in Text Emily Pitler and Ani Nenkova Computer and Information Science University of Pennsylvania Philadelphia PA 19104 USA epitler nenkova@ Abstract Discourse connectives are words or phrases such as once since and on the contrary that explicitly signal the presence of a discourse relation. There are two types of ambiguity that need to be resolved during discourse processing. First a word can be ambiguous between discourse or non-discourse usage. For example once can be either a temporal discourse connective or a simply a word meaning formerly . Secondly some connectives are ambiguous in terms of the relation they mark. For example since can serve as either a temporal or causal connective. We demonstrate that syntactic features improve performance in both disambiguation tasks. We report state-of-the-art results for identifying discourse vs. non-discourse usage and human-level performance on sense disambiguation. 1 Introduction Discourse connectives are often used to explicitly mark the presence of a discourse relation between two textual units. Some connectives are largely unambiguous such as although and additionally which are almost always used as discourse connectives and the relations they signal are unambiguously identified as comparison and expansion respectively. However not all words and phrases that can serve as discourse connectives have these desirable properties. Some linguistic expressions are ambiguous between DISCOURSE AND NON-DISCOURSE USAGE. Consider for example the following sentences containing and and once. This work was partially supported by NSF grants IIS-0803159 IIS-0705671 and IGERT 0504487. la Selling picked up as previous buyers bailed out of their positions and aggressive short sellers- anticipating further declines-moved in. lb My favorite colors are blue and green. 2a The asbestos fiber crocidolite is unusually resilient once it enters the lungs with even brief .