Complements And Adjuncts In Dependency Grammar Parsing Emulated By A Constrained Context-Free Grammar

Generalizing from efforts parsing natural language sentences using the grammar formalism, Dependency Grammar (DG) has been emulated by a context-free grammar (CFG) constrained by grammatical function annotation. Single-headedness and projectivity are assumed. This approach has the benefit of making general constraint-based context-free grammar parsing facilities available to DG analysis. This paper describes an experimental implementation of this approach using unification to realize grammatical function constraints imposed on a dependency structure backbone emulated by a context-flee grammar. Treating complements of a head word using subcategoHzation lists residing in the head word makes it possible to keep phrase-structure-rule-like mechanisms to the minimum. Adjuncts are treated with a syntactic mechanism that does not reside in the lexicon in this generally lexical approach to grammar. I n t r o d u c t i o n The mathematical properties of Dependency Grammar (Tesniere (1959)) are studied by Gaifman (1965) and Hays (1964). Following their footsteps, Robinson (1970) formulates four axioms to govern the weU-formedness of dependency structures: (a) One and only one element is independent; (b) All others depend directly on some element; (c) No element depends directly on more than one other;, (d) If A depends directly on B and some element C intervenes between them (in linear order ofs~ing), then C depends directly on A or on B or some other intervening element. These axioms require that all words should depend on only one word and that, arranging words in linear order, crossing of dependency links as in Fig.l should not be allowed. Yuyanxue linguistics wo zhidao ta xihuan I know he likes