Prolog and natural-language analysis
Prolog and natural-language analysis
The equivalence of four extensions of context-free grammars
Mathematical Systems Theory
The interface between phrasal and functional constraints
Computational Linguistics
ACL '83 Proceedings of the 21st annual meeting on Association for Computational Linguistics
The structure of shared forests in ambiguous parsing
ACL '89 Proceedings of the 27th annual meeting on Association for Computational Linguistics
Lfg generation by grammar specialization
Computational Linguistics
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Recently researchers working in the LFG framework have proposed algorithms for taking advantage of the implicit context-free components of a unification grammar [Maxwell and Kaplan, 1996]. This paper clarifies the mathematical foundations of these techniques, provides a uniform framework in which they can be formally studied and eliminates the need for special purpose runtime datastructures recording ambiguity. The paper posits the identity: Ambiguous Feature Structures = Grammars, which states that (finitely) ambiguous representations are best seen as unification grammars of a certain type, here called "interactionfree" grammars, which generate in a backtrackfree way each of the feature structures subsumed by the ambiguous representation. This work extends a line of research [Billot and Lang, 1989; Lang, 1994] which stresses the connection between charts and grammars: a chart can be seen as a specialization of the reference grammar for a given input string. We show how this specialization grammar can be transformed into an interaction-free form which has the same practicality as a listing of the individual solutions, but is produced in less time and space.