Case Role Filling As A Side Effect Of Visual Search

This paper addresses the problem of generating communicatively adequate extended responses in the absence of specific knowledge concerning the intensions of the questioner. We formulate and justify a heuristic for the selection of optional deep case slots not contained in the question as candidates for the additional information contained in an extended response. It is shown that, in a visually present domain of discourse, case role filling for the construction of an extended response can be regarded as a side effect of the visual search necessary to answer a question containing a locomotion verb. The paper describes the various representation constructions used in the German language dialog system HAMANS for dealing with the semantics of locomotion verbs and illustrates their use in generating extended responses. In particular, we outline the structure of the geometrical scene description, the representation of events in a logic-oriented semantic representation language, the case-frame lexicon and the representation of the referential semantics based on the Flavor system. The emphasis is on a detailed presentation of the application of object-oriented programming methods for coping with the semantics of locomotion verbs. The process of generating an extended response is illustrated by an extensively annotated trace.