A constraint-based model for lexical and syntactic choice in natural language generation

In this paper, we show how a constraint-based approach influences the modeling of (1) preposition lexicalization and of (2) the choice of syntactic structure in natural language generation (in particuler in French). We concentrate on the linguistic description, which is the most challenging. The CSP procedures themselves are then rather straightforward. In the first case, preposition choice depends on the verb and its requirements, on the one hand, and the characteristics of the NP the preposition heads, on the other hand. In the second case, the choice of a particular syntactic structure depends on syntactic, semantic and pragmatic constraints on a verb, its arguments and on the parameters of the semantic representation. These dependencies may induce somewhat contradictory expectations. A constraint-based approach introduces a declarative model of these complex relations, allowing to identify all the possible (1) lexical choices or (2) syntactic structures which can be predicted from lexical descriptions.