Information-based Case Grammar

In this paper we propose a framework of Informationbased Case Grammar (ICG). This grammatical formalism entails that the lexical entry for each word contain both semantic and syntactic feature structures. In the feature structure of a phrasal head, we encode syntactic and semantic constraints on grammatical phrasal patterns in terms of thematic structures, and encode the precedence relations in terms of adjunct structures. Such feature structures denote partial information which defines the set of legal phrases. They also provide sufficient information to identify thematic roles. With this formalism, parsing and thematic analysis can be achieved simultaneously. Due to the simplicity and flexibility of Information-based Case Grammar, context dependent and discontinuous relations such as agreements, coordinations, long-distance dependencies, and control and binding, can be easily expressed. ICG is a kind of unification-based formalism. 'H:erefore it inherits the advantages of unification-bmscd formalisms and more. In the feature structure of a phrasal head, we encode syntactic and semantic constraints on grammatical phrasal patterns ha terms of thematic structures, and encode the precedence relations in terms of adjunct structures. The feature structure of a potential phr~al head denotes partial information for defining the set of legal/grammatical phrases. It also provides enough information to identify the thematic roles for arguments and adjuncts [Chert 89]. In other words, with ICG, parsing and thematic analysis are achieved simultaneously without additional operation; and generation with thematic structure can be done with the identical formalism. We take Mandarin Chinese as our representational target. Thus, the features were selected to account for Chinese only. Itowever, the abstract design of this formalism is not limited to only the representation of Chinese. Since the Chinese lexicon is impoverished in inflection, it is necessary to fully stipulate both semantic and syntactic information for the purpose of both parsing and generation. Furthermore the precedence relationship of constituents is defined over thematic roles. This seems to be more appropriate for Chinese. By coincidence, Bresnen and Kanerva's [Bresnan 89] lexical mapping theory represents a shift towards the possibility of senmntics major approaches.