An HPSG Account of the Hierarchical Clause Formation in Japanese : HPSG-Based Japanese Grammar for Practical Parsing

The most perspicuous phenomenon that demonstrates the head-final property of Japanese is the sentence-final clusters of auxiliary verbs such as (s)ase and conjunctive particles nagara. Although they are related to the hierarchical clause structure that has been discussed in the literature of Japanese linguistics, the hierarchical complexities have also been one of the major causes of the failure of long sentence parsing in the field of natural language processing. To overcome this parsing problem, we develop Japanese Phrase Structure Grammar, NAIST JPSG, which is a partial implementation of ideas from not only recent developments in Headdriven Phrase Structure Grammar but also Minami's four-level syntactic/semantic hierarchy. We devote our discussion to the analysis of hierarchical clause formation, pseudo-lexical treatment of causatives and regulation of co-occurrence of subordinate clauses, with main focus on their specific lexical information of the sentence-final clusters. Causative constructions exhibit properties of simple/complex thematic relation in spite of their morphologically simple status. A clause can be embedded as subordinate clause if and only if the clause is a member of the same or lower level in Minami's sense than the main clause belongs to. These hierarchical clause phenomena can be explained by introducing lexical description and general mechanism assumed in JPSG.