tailieunhanh - Báo cáo khoa học: "A Hierarchical Account of Referential Accessibility"

In this paper, we outline a theory of referential accessibility called Veins Theory (VT). We show how VT addresses the problem of "left satellites", currently a problem for stack-based models, and show that VT can be used to significantly reduce the search space for antecedents. We also show that VT provides a better model for determining domains of referential accessibility, and discuss how VT can be used to address various issues of structural ambiguity. | A Hierarchical Account of Referential Accessibility Nancy IDE Department of Computer Science Vassar College Poughkeepsie New York 12604-0520 USA ide@ Dan CRISTEA Department of Computer Science University Al. I. Cuza Iasi Romania dcristea@ Abstract In this paper we outline a theory of referential accessibility called Veins Theory VT . We show how VT addresses the problem of left satellites currently a problem for stack-based models and show that VT can be used to significantly reduce the search space for antecedents. We also show that VT provides a better model for determining domains of referential accessibility and discuss how VT can be used to address various issues of structural ambiguity. Introduction In this paper we outline a theory of referential accessibility called Veins Theory VT . We compare VT to stack-based models based on Grosz and Sidner s 1986 focus spaces and show how VT addresses the problem of left satellites . subordinate discourse segments that appear prior to their nuclei dominating segments in the linear text. Left-satellites pose a problem for stack-based models which remove subordinate segments from the stack before pushing a nuclear or dominating segment thus rendering them inaccessible. The percentage of such cases is typically small which may account for the fact that their treatment has been largely overlooked in the literature but the phenomenon nonetheless persists in most texts. We also show how VT can be used to address various issues of structural ambiguity. 1 Veins Theory Veins Theory VT extends and formalizes the relation between discourse structure and reference proposed by Fox 1987 . VT identifies veins over discourse structure trees that are built according to the requirements put forth in Rhetorical Structure Theory RST Mann and Thompson 1987 . RST structures are represented as binary trees with no loss of information. Veins are computed based on the RST-specific distinction between nuclei and .