A parsing algorithm for unification grammar
Computational Linguistics
Constraint-based grammar formalisms: parsing and type inference for natural and computer languages
Constraint-based grammar formalisms: parsing and type inference for natural and computer languages
An efficient context-free parsing algorithm
Communications of the ACM
Left-corner parsing algorithm for unification grammars
Left-corner parsing algorithm for unification grammars
An efficient implementation of the head-corner parser
Computational Linguistics
Using restriction to extend parsing algorithms for complex-feature-based formalisms
ACL '85 Proceedings of the 23rd annual meeting on Association for Computational Linguistics
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Shieber's abstract parsing algorithm (Shieber 1992) for unification grammars is an extension of Earley's algorithm (Earley 1970) for context-free grammars to feature structures. In this paper, we show that, under certain conditions, Shieber's algorithm produces what we call a nonminimal derivation: a parse tree which contains additional features that are not in the licensing productions. While Shieber's definition of parse tree allows for such nonminimal derivations, we claim that they should be viewed as invalid. We describe the sources of the nonminimal derivation problem, and propose a precise definition of minimal parse tree, as well as a modification to Shieber's algorithm which ensures minimality, although at some computational cost.