tailieunhanh - Báo cáo khoa học: "A UNIFICATION-BASED PARSER FOR RELATIONAL GRAMMAR"

We present an implemented unification-based parser for relational grammars developed within the s t r a t i f i e d f e a t u r e g r a m m a r (SFG) framework, which generalizes Kasper-Rounds logic to handle relational grammar analyses. We first introduce the key aspects of SFG and a lexicalized, graph-based variant of the framework suitable for implementing relational grammars. We then describe a head-driven chart parser for lexicalized SFG. The basic parsing operation is essentially ordinary feature-structure unification augmented with an operation of label unification to build the stratified features. | A UNIFICATION-BASED PARSER FOR RELATIONAL GRAMMAR David E. Johnson IBM Research Division . Box 218 Yorktown Heights NY 10598 djohns@ Adam Meyers Linguistics Department New York University New York NY 10003 meyers@ Lawrence s. Moss Mathematics Department Indiana University Bloomington IN 47401 lmoss@ Abstract We present an implemented unification-based parser for relational grammars developed within the stratified feature grammar SFG framework which generalizes Kasper-Rounds logic to handle relational grammar analyses. We first introduce the key aspects of SFG and a lexicalized graph-based variant of the framework suitable for implementing relational grammars. We then describe a head-driven chart parser for lexicalized SFG. The basic parsing operation is essentially ordinary feature-structure unification augmented with an operation of label unification to build the stratified features characteristic of SFG. INTRODUCTION Although the impact of relational grammar RG on theoretical linguistics has been substantial it has never previously been put in a form suitable for computational use. RG s multiple syntactic strata would seem to preclude its use in the kind of monotonic unification-based parsing system many now consider standard 1 11 . However recent work by Johnson and Moss 2 on a Kasper-Rounds KR style logic-based formalism 5 for RG called stratified Feature Grammar SFG has demonstrated that even RG s multiple strata are amenable to a feature-structure treatment. Based on this work we have developed a unification-based chart parser for a lexical version of SFG suitable for building computational relational grammars. A lexicalized SFG is simply a collection of stratified feature graphs S-graphs each of which is anchored to a lexical item analogous to lexicalized TAGs 10 . The ba sic parsing operation of the system is S-graph unification S-unification This is essentially ordinary feature-structure unification augmented with an

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