Free Word Order in a Constraint-based Implementation of Dependency Grammar

Parsing of sentences based on Dependency Grammar is emulated with a constraintand unification-based mechanism that preserves single-headedness and projectivity in syntactic dependency. Working on Chinese, and referring to English at times, the authors have treated subcategorization properties of verbs on the assumptions that relative positions of obligatory complements of a verb are fixed, and that optional verbal adjuncts, while relatively free in their choice of positions in the sentence, are constrained to be placed farther away from the governing verb than any complements. A pair of subcategorization lists residing in the governing verb have been used to capture these properties. However when one tries to extend the model to languages with relatively free word order like Japanese, for which the assumptions mentioned above are not valid, straight-forward list-manipulations on subcategorization lists will not be adequate. This paper discusses how additional subcategorization handling mechanisms can be introduced to deal with verbal complements scrambling and intervening adjuncts, while retaining the mechanisms to capture default word order.