F-PATR: A Functional Constraints for Unification-Based Grammars
نویسنده
چکیده
Motivation for including relational constraints other than equality within grammatical formalisms has come from discontinuous constituency and partially free word order for natural languages as well as from the need to define combinatory operations at the most basic level for languages with a two-dimensional syntax (e.g., mathematical notation, chemical equations, and various diagramming languages). This paper presents F-PATR, a generalization of the PATR-II unification-based formalism, which incorporates relational constraints expressed as user-defined functions. An operational semantics is given for unification that is an adaptation and extension of the approach taken by Ait-Kaci and Nasr (1989). It is designed particularly for unificationbased formalisms implemented in functional programming environments such as Lisp. The application of unification in a chart parser for relational set languages is discussed briefly.
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