tailieunhanh - Báo cáo khoa học: "COORDINATION INUNIFICATION-BASED GRAMMARS"

Within unification-based grammar formalisms, providing a treatment of cross-categorial coordination is problematic, and most current solutions either over-generate or under-generate. In this paper we consider an approach to coordination involving "composite" feature structures, which describe coordinate phrases, and present the augmentation to the logic of feature structures required to admit such feature structures. | COORDINATION IN UNIFICATION-BASED GRAMMARS Richard p. Cooper Department of Psychology University College London London WC1E 6BT . JANET ucjtrrc@ ABSTRACT Within unification-based grammar formalisms providing a treatment of cross-categorial coordination is problematic and most current solutions either over-generate or under-generate. In this paper we consider an approach to coordination involving composite feature structures which describe coordinate phrases and present the augmentation to the logic of feature structures required to admit such feature structures. This augmentation involves the addition of two connectives composite conjunction and composite disjunction which interact to allow crosscategorial coordination data to be captured exactly. The connectives are initially considered to function only in the domain of atomic values before their domain of application is extended to cover complex feature structures. Satisfiability conditions for the connectives in terms of deterministic finite state automata are given both for the atomic case and for the more complex case. Finally the Prolog implementation of the connectives is discussed and it is illustrated how in the atomic case and with the use of the freeze 2 predicate of second generation Prologs the connectives may be implemented. The Problem Given a modern unification-based grammar such as HPSG or PATR FUG-style grammars where feature structure descriptions are associated with the constituents of the grammar and unification is used to build the descriptions of constituents from those of their subconstituents providing a treatment of coordination especially cross-categorial coordination is problematic. It is well known that coordination is not restricted to like categories see 1 so it is too restrictive to require that the syntactic category of a coordinate phrase be just the unification of the syntactic categories of the conjuncts. Indeed the data suggest that the syntactic categories of the .