tailieunhanh - Báo cáo khoa học: "Multi-Component TAG and Notions of Formal Power"

This paper presents a restricted version of Set-Local Multi-Component TAGs Weir, 1988 which retains the strong generative capacity of Tree-Local MultiComponent TAG . produces the same derived structures but has a greater derivational generative capacity . can derive those structures in more ways . This formalism is then applied as a framework for integrating dependency and constituency based linguistic representations. | Multi-Component TAG and Notions of Formal Power Mark Dras Inst for Research in Cognitive Science University of Pennsylvania Suite 400A 3401 Walnut Street Philadelphia PA 19104-6228 William Schuler David Chiang Computer and Information Science University of Pennsylvania Philadelphia PA 19104 schuler dchiang @ Abstract This paper presents a restricted version of Set-Local Multi-Component TAGs Weir 1988 which retains the strong generative capacity of Tree-Local MultiComponent TAG . produces the same derived structures but has a greater derivational generative capacity . can derive those structures in more ways . This formalism is then applied as a framework for integrating dependency and constituency based linguistic representations. 1 Introduction An aim of one strand of research in generative grammar is to find a formalism that has a restricted descriptive capacity sufficient to describe natural language but no more powerful than necessary so that the reasons some constructions are not legal in any natural language is explained by the formalism rather than stipulations in the linguistic theory. Several mildly context-sensitive grammar formalisms all characterizing the same string languages are currently possible candidates for adequately describing natural language however they differ in their capacities to assign appropriate linguistic structural descriptions to these string languages. The work in this paper is in the vein of other work Joshi 2000 in extracting as much structural descriptive power given a fixed ability to describe strings and uses this to model dependency as well as constituency correctly. One way to characterize a formalism s descriptive power is by the the set of string languages it can generate called its weak generative capacity. For example Tree Adjoining Grammars TAGs Joshi et al. 1975 can generate the language anbncndn and Context-Free Grammars CFGs cannot Joshi 1985 . Figure 1 CFG-generable

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