TAILIEUCHUNG - Báo cáo khoa học: "A Language for the Statement of Binary Relations over Feature Structures"

Unification is often the appropriate method for expressing relations between representations in the form of feature structures; however, there are circumstances in which a different approach is desirable. A declarative formalism is presented which permits direct mappings of one feature structure into another, and illustrative examples are given of its application to areas of current interest. | A Language for the Statement of Binary Relations over Feature Structures Graham Russell Afzal Ballim Dominique Estival Susan Warwick-Armstrong ISSCO 54 rte. des Acacias 1227 Geneva Switzerland elu@ Abstract Unification is often the appropriate method for expressing relations between representations in the form of feature structures however there are cữcumstances in which a different approach is desirable. A declarative formalism is presented which permits dữect mappings of one feature structure into another and illusfia-tive examples are given of its application to areas of current interest. 1. Introduction Benefits arising from the adoption of unification as a tool in computational linguistics are well known a declarative monotonic method of combining partial information expressed in data structures convenient for linguistic applications permits the writing of sensible grammars that can be made independent from processing mechanisms and a growing familiarity in both theoretical and computational circles with the techniques of unification fosters fruitful interchange of ideas and experiences. There are however occasions when unification alone is not an appropriate tool. In essence unification is a ternary relation in which two structures when merged form a third it is less attractive in ck-cumstances where the relation to be expressed is binary - when one would like to manipulate a single feature structure FS perhaps simulating the direct transformation of one FS into another. 1 The present paper introduces a declarative formalism intended for the expression of such relations and shows how it may be applied to some areas of current interest. The formalism in question is based upon a notion of transfer rule informally a set of such rules may be considered as characterizing We are indebted to Jacques Jayez for comments on an earlier draft of this paper. 1 Clearly there is a sense in which such relations can be viewed as ternary T Ft R F2 where F and F2

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