Discourse Context Context and Natural Language

We discuss the problems of developing a theory of context that applies to the phenomena of naturally occurring discourse and that might be useful in assisting with the problems that arise in generating and interpreting discourse. The theories of context that have recently emerged in AI treat context as a determinant of literal meaning. This idea does in fact t some natural language phenomena. But we suggest (1) that the account is inadequate for important eeects that occur in discourse, and moreover (2) in discourse, the mutuality of context provides important constraints on the dynamics of context. We explore these ideas in the paper, and also describe an ongoing project that seeks to develop an empirically adequate and computationally useful approach to the problem of contextual eeects on inference in discourse. Readers, please note that this is a provisional draft that describes ongoing work. Old and new theories of context In both the philosophical and computational literature, much has been made of the importance of context in natural language interpretation. The theories of context that have been developed in this connection (for instance, in (3), (3), (3), and (3)) have stressed the part it plays in determining the meaning of natural language expressions. The recent work on context that is being carried out in AI has much in common with the earlier work in philosophical logic, though it does not seem to draw directly on this work. The two approaches share the basic idea that context is an interpretation-shifting mechanism. David Kaplan's theory provides a good representative version of the basic idea. The theory is connned to the indexicals`I', `here', and`now'. In this case, a context can be modeled as a triple consisting of a person , a place and a time; these values then determine the interpretation of the corresponding indexicals. In at least one way, Kaplan's work is more sophisticated than the work on context that is emerging in AI| this is the distinction between content and character that emerges from his explanation of how a sentence likèI am here now' can be valid, whilèI might not have been here now' can also be true. Kaplan's analysis shows that there are systematic variations between the contextual indices that innuence interpretation of expressions, and the modal indices that keep track of diierences in the facts that determine the truth values of interpreted expressions. One of the chief accomplishments of …