tailieunhanh - Báo cáo khoa học: "DECLARATIVE k VIEV NOOEL FOR DEPENDENCY PARSING INTO BLACKBOARD METHOOOLOGY"

Recently, we have augmented the dependency parsing model t o c o v e r a l s o tong-distance dependencies. According to the augmented model we have implemented a blackboard-based dependency p a r s e r ADP (Augmented Dependency P a r s e r ) . | DECLARATIVE MODEL FOR DEPENDENCY PARSING -A VIEW INTO BLACKBOARD METHODOLOGY Valkonen K. Jappinen X. Lehtola A. and Ylflammi M. KIELIKONE-project SITRA Foundation 329 SF-00121 Helsinki Finland tel. inti 358 0 641 877 ABSTRACT This paper presents a declarative dependency constraint model for parsing an inflectional free word order language like Finnish. The structure of Finnish sentences is described as partial dependency trees of depth one. Parsing becomes a nondeterministic search problem in the forest of partial parse trees. The search process is able to solve also ambiguities and long-distance dependencies. Parsing is controlled by a blackboard system. A working parser for Finnish has been implemented based on the model. 1 INTRODUCTION The development of our computational model for dependency parsing has progressed in three parallel and interrelated phases 1 The development of a perspicuous high level grammar specification language which grasps well regularities and idiosyncracies of inflectional free word order languages. 2 The acquisition of a grammar using that language as the description media. 3 The development of a parsing strategy and a compiler for the specification language. In our first approach the parsing process is described as a sequence of local decisions Nelimarkka et al. 1984 . A pair of adjacent structures of an input sentence is connected if there exists a valid binary dependency relation between them. Binary relations are boolean expressions of the morphological and syntactic restrictions on argument structures. In that first version dependency sructures were modelled procedurally with finite two-way automata Lehtola et al. 1985 . Grammar descriptions turned out to be complicated to handle and due to purely local decisions some global phenomena such as long-distance dependencies were not analyzed. A new grammar description formalism and computational method was developed a declarative high level language FUNDPL JSppinen et al. 1986 .