A Declarative Grammar Formalism For Dependency Grammar

Author: Ralph Debusmann

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Beginning with the groundbreaking work of Chomsky in the 1950s, syntactians have concentrated mostly on the English language. But English is not a typical natural language: in particular, its word order is very rigid, as opposed to most other languages which exhibit freer word order. The phrase structure-based approach employed for the analysis of English runs into severe problems when confronted with freer word order languages. Aside from the mainstream, linguists in Eastern Europe and Japan have pursued an approach to syntax which seemed better suited for the analysis of freer word order languages: dependency grammar. The key asset of dependency grammar is that it allows for a clean separation of syntactic dependency and surface word order. Unfortunately, none of the frameworks for dependency grammar has really caught on. We suggest two reasons for their failure: a) many of the dependency-based frameworks lack proper formalization and, perhaps surprisingly, b) most of them lack a realistic and workable account of word order. In this thesis, we try to remedy these problems in the setting of a constraint-based approach to dependency grammar based on \citeDuchier99. We present a new account of word order for dependency grammar couched in a declarative grammatical formalism called Topological Dependency Grammar (TDG). TDG allows to cleanly separate the two levels of syntactic dependency and surface word order, which greatly facilitates the conception of grammars for freer word order languages. In addition, we can efficiently parse with TDG grammars: using a reduction described in \citeDuchier00, we achieved an efficient parser implementation using modern constraint programming techniques.