A formal computational semantics and pragmatics of speech acts

This paper outlines a formal computational semantics and pragmatics of the major speech act types. A theory of force is given that allows us to give a semantically and pragmaticaly motivated taxonomy of speech acts. The relevance of the communication theory to complex distributed artificial intellince, DAI, systems is described. l Introduction In a system that engages in a dialogue with a user about some domain, like the one we are building in the WISBER project [Bergmann, Gerlaoh 87], the problem of describing the meaning of a speech act in terms of its effect on the user model and, more generally, on the system's knowledge base becomes central. The fundamental problem is that, until now, there has been no general formal theory of meaning for speech acts. Previous formal semantic theories such as Montague [74] and situation semantics [Barwise and Perry 83] were limited to assertions. Cohen and Perrault [79] give only a theory of how speech actsare planned, the semantics being implicit in the add and delete lists of the operators. Appelt [85] gives a semantics for assertions based on Moore [80] that is compatible with our approach. However, there is no explicit theory of communication. As Appelt himself states, what is lacking is an explicit theory of intention. Searle and Vanderveken [85] do little more than classHy speech acts based on features that were seen as relevant to their differentiation. However, as we will argue below, those features are not motivated by any coherent theory of meaning. The crucial features that define force are left unanalyzed. None of the above theories give a formal semantics for nonassertive speech acts. As Searle also states, what is missing is formal theory of iutentions. In this paper we outline a formal semantics and pragmatics of speech acts based on an explicit formal theory of information and intention. A formal description /0f the notion ofillocutionary force is given. We take a new look at Searle's a classification of speech acts. In the process, we develop a deeper understanding of the rather vague notion of force. We start with Searle's classification of illocutionary acts. Searle and Vanderveken's definition of force is criticized. Next Habermas is criticized. Next, referential theories of meaning are looked at critically. Then we present our theory of the semantics and pragmatics of speech acts. We then use that theory to give a theory of force. We then describe the …