Contextually enriched argument linking
In this article we investigate the role played by one aspect of context, namely encyclopedic knowledge, in the interpretation of clause arguments. We discuss cases where the assignment of a specific semantic role of a predicate to a clause argument is not determined by the grammar alone, but requires extragrammatical resources (in particular, world knowledge), and then present a formally explicit analysis of the interaction of grammar and world knowledge in the linking of clause arguments to specific semantic roles. The analysis of this interaction is based on the hypothesis that semantic composition consists in the identification of the referents introduced by NPs with the participants involved in the states of affairs described by predicates, with both referents and participants being represented by means of free variables. The contribution of the grammatical resources to the identification of free variables is captured by means of referent systems which essentially associate with each free variable the morphosyntactic information relevant for its identification. Two variables x and y can be identified (i.e. we can add the equation <i>x</i> = <i>y</i> to the discourse representation structure) if they are associated with the same (or matching) information. The contribution of extragrammatical resources to the identification of free variables is modeled in terms of abductive reasoning based on encyclopedic knowledge.