TAILIEUCHUNG - Báo cáo khoa học: "Head-Driven Generation with HPSG"

As HPSG is head-driven, with clear semantic heads, semantic head-driven generation should be simple. We adapt van Noord's Prolog generator for use with an HPSG grammar in ProFIT. However, quantifiers and context factors are difficult to include in headdriven generation. We must adopt recent theoretical proposals for lexicalized scoping and context. With these revisions, head-driven generation with HPSG is not so simple, but it is possible. | Head-Driven Generation with HPSG Graham Wilcock Centre for Computational Linguistics University of Manchester Institute of Science and Technology PO Box 88 Manchester M60 1QD United Kingdom Abstract As HPSG is head-driven with clear semantic heads semantic head-driven generation should be simple. We adapt van Noord s Prolog generator for use with an HPSG grammar in ProFIT. However quantifiers and context factors are difficult to include in head-driven generation. We must adopt recent theoretical proposals for lexicalized scoping and context. With these revisions head-driven generation with HPSG is not so simple but it is possible. 1 Introduction A natural approach to generation with Head-driven Phrase Structure Grammar Pollard and Sag 1994 is to use a head-driven algorithm. HPSG is head-driven not only syntactically but also semantically. While the Head Feature Principle requires identity of major syntactic features between a phrase and its syntactic head daughter the Semantics Principle in various formulations requires identity of major semantic features between a phrase and its semantic head daughter. Since the semantic head is very clearly defined in HPSG semantic head-driven generation should be easy to implement. Efficient head-driven generation algorithms such as BUG SHD and CSHD have been presented as Prolog algorithms for use with DCG grammars. In Section 2 we briefly describe how an HPSG grammar can be implemented as a PSG with typed feature structures which can be compiled into a DCG by the ProFIT system. In this way HPSG grammars can be used with the existing Prolog algorithms. Such a combination of head-driven grammar and head-driven generator works well if the semantics is strictly head-driven. However in Section 3 we show that if we implement the HPSG textbook semantics with quantifier storage and contextual background conditions the notion of semantic head becomes unclear and this approach no longer works. In fact head-driven .

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