An Integrated Framework for Semantic and Pragmatic Interpretation

We report on a mechanism for semantic and pragmatic interpretation that has been designed to take advantage of the generally compositional nature of semantic analysis, without unduly constraining the order in which pragmatic decisions are made. To achieve this goal, we introduce the idea of a conditional interpretation: one that depends upon a set of assumptions about subsequent pragmatic processing. Conditional interpretations are constructed compositionally according to a set of declaratively specified interpretation rules. The mechanism can handle a wide range of pragmatic phenomena and their interactions. 1 I n t r o d u c t i o n Compositional systems of semantic interpretation, while logically and computationally very attractive [6,20,26], seem unable to cope with the fact that the syntactic form of a a utterance is not the only source of information about its meaning. Contextual information--information about the world and about the history of a discourse-influences not only an utterance's meaning, but even its preferred syntactic analysis [3,5,7,16]. Of course, context also influences the interpretation (or meaning in context) of the utterance, in which, for example, referring expressions have been resolved. One possible solution is to move to an integrated system of semantic and pragmatic interpretation, defined recursively on syntactic analyses that are 1 This research has been funded by DARPA under Contract N00039-84-C-0524, and by a gift from the Systems Development Foundation as par t of a coordinated research effort with the Center for the Study of Language and Information, Stanford University. We would like to thank David Israel, FLay Perrault, and Stuart Shieber for their helpful discussions regarding this work. neutral about those decisions that depend upon context. In this approach, a least-commitment grammar may be used to produce neutral representations that can be reconfigured later. Such a grammar might, for example, leave quantifiers in place [30], at tach all prepositional phrases low and right [22], and bracket to the right all compound nominals. 2 These neutral analyses can then serve as input to a system that produces interpretations (and not meanings) in a nearly compositional manner, in that the interpretation of a phrase a is a function of the interpretations of its syntactic constituents together with its context of utterance. This model of semantic interpretation assumes that contextual information is available whenever it is needed for deciding among alternative interpretations. However, this is often not the case: questions about the interpretation of some constituent of an utterance might be answerable only when information about the interpretation of syntactically distant constituents becomes available. Familiar examples of this can be found, for instance, in sentences with quantifier scoping ambiguities and in sentences that include intrasentential anaphora. The so-called donkey sentences [9] exhibit both these phenomena. These difficulties do not necessitate a complete abandonment of compositionality. To take advantage of the generally compositional nature of semantic analysis without constraining unduly the order in which pragmatic decisions are made, we assign to phrases conditional interpretations, 2Tllere are reasons to suspect that ultinmtely syntactic analysis should be incorporated into the same stage of processing as semantic and pragnuLtic analysis; in particular, it is difficult to develop syntactically neutral representations for certain constructions such as conjunction. 3For simplicity, we shall use the term "phrase" to refer bo th to an entire utterance and to a constituent of an utterance, distinguishing betweeal the two only when needed.