A Simple String-Rewriting Formalism For Dependency Grammar

Recently, dependency grammar has gained renewed attention as empirical methods in parsing have emphasized the importance of relations between words, which is what dependency grammars model explicitly, but context-free phrase-structure grammars do not. While there has been much work on formalizing dependency grammar and on parsing algorithms for dependency grammars in the past, there is not a complete generative formalization of dependency grammar based on string-rewriting in which the derivation structure is the desired dependency structure. Such a system allows for the definition of a compact parse forest in a straightforward manner. In this paper, we present a simple generative formalism for dependency grammars based on Extended Context-Free Grammar, along with a parser; the formalism captures the intuitions of previous formalizations while deviating minimally from the much-used Context-Free Grammar.