A Common Framework For Analysis And Generation

It seems highly desirable to use a single representation of linguistic knowledge for both analysis and generation. We argue that the only part of the average NL system's knowledge that we can have any faith in is its vocabulary and, to a lesser extent , its syntactic rules, and we investigate the consequences of this for generation. 1 ANALYSIS Consider a typical NLU system. You give it a piece of text, say: (1) The house I live in is damp. It grinds away, trying out syntactic rules until it has an analysis of the structure of the text. The syntactic rules incorporate a semantic element , which automatically builds up a representation of the meaning of the text in some appropriate formal language-something like the follow-Exactly what formal language you choose for the representation of meaning will depend on a number of things, notably on the intended application (if any) of the system, on the availability of automatic inference systems for the language in question, and on the perceived need for expressive power. For the system that lies behind the discussion in this paper we chose a version of Turner's [1987] property theory. The details of property theory do not really matter very much here. What matters is that any attempt to give a complete formal paraphrase of (1) must include at least as much information as we have given above. In particular, the logical structure of our paraphrases contains essential information (about, for instance, the differences between objects which are introduced in the utterance and ones whose existence is presupposed), even if there is still considerable debate about the best way of representing this information. 2 GENERATION Suppose we have the formula given above as a formal paraphrase of (1), and we want to generate an English sentence which corresponds to it. We might hope to use our syntactic/semantic rules "backwards", looking for something which would generate a sentence and whose semantic component could be made to match the given sequence. The final rule we actually used in our analysis of (1) is an elaboration of the standard S-, NP VP rule which contains a description of how the meanings of the NP and the VP should be combined to obtain the meaning of the NP. Space does not permit inclusion of this rule. The important point for our present purposes is that the representation of the meaning of …