The Definite Article: Code and Context

Numerous grammatical items can only be understood if the context is taken into account. In order to provide a formal treatment of this problem, we introduce the nonon of knowledge base into linguistics. After having worked out a hard core system of rules for analysing numerals, definite articles, and indefinite articles, we give a thorough study of the French singular definite article le. This grammatical item has the particularity of not encoding a fixed information stored in the lexicon, but of running a program ofinformation processing We show that the referential computation can be made by a precise algorithm working on a definite stratum of the reader's knowledge base. In this framework, the uniqueness hypothesis of Russell becomes a guideline to retrieve memorized information. The algorithm accounts for deictic as well as anaphoric referential identifications. Our analysis proposes a unitary account for a large part of empirical data and reconciles the logical approach of Russell-Montague with the pragmatic approach of Hawkins. o I N T R O D U C T I O N What is the difference between grammatical items and other words of the language? Is the semantic value of the article the in the noun phrase the table of the same nature as that of the noun table? To answer this question, we shall not take the point of view of linguists who consider that the essential job of linguistics is only to build logical representations of sentences. This is because we believe that the meaning of an expression cannot only be in its logical representation. It seems more likely to be the product of a dynamic processing of information.This is why we attribute two complementary tasks to semantics: (i) building semantic representations of a logical nature; (2) handling these representations in specific cognitive contexts. In the recognition stage, the parser builds the semantic representations with the support of the syntactical structures. This relation between syntax and logic was first established on formal grounds by Montague, and remains an ideal for us to reach in semantics, as the beautiful book of Kamp & Reyle (1993) testifies. But to narrow semantics to this construction stage has always seemed insufficient to us. Why should we construct formulas if we then have no use for them? We would like to avoid producing formulas without any operational force. To be effective, these representations have to be brought into play to 140 The Definite Article: Code and Context account for inferences and dialogues. Moreover, they must be able to be subjected to empirical tests. All the empirical data we can gather on any linguistic problem (such as time, quantification, etc.) do not determine in a unique fashion what the best representations are. Semantic theory is undetermined by observation. To overcome these insufficiencies, we thought it necessary to borrow the notion of a knowledge base from artificial intelligence. It is a memory where not only the representations of the sentences analysed are recorded but also extralinguistic knowledge (whether accepted or tacitly possessed by the hearer at speech time). The model also contains a reasonable module which makes it possible to draw inferences and compute answers to questions by using the techniques of resolution by unification. We thus have the means to distinguish clearly between the semantic representation of an expression and its meaning. We understand the meaning of an utterance as the whole set of inferences one can obtain after entering its semantic representation into the knowledge base. Once an implementation of this model has been devised, it becomes possible to simulate dialogues. We enter a small text into the computer and we ask questions: who does what? when? etc. Then, since to understand a text is to be able to answer questions on that text, it becomes possible to test semantic hypotheses empirically: the best hypothesis is the one that gives the best simulation of a dialogue. We used this model to give linguistic analyses of spatio-temporal expressions in Chinese (Renaud 1988) and in French (Renaud, forthcoming). And when we began to study nominal determiners in French some years ago, we discovered that here, too, the notion of a knowledge base has a leading part to play in their semantic interpretation. It is a truism in linguistics to consider that meaning depends on context. There are countless examples of starred (inacceptable) sentences which, when provided with an adequate context, become perfectly acceptable. This banal observation is wholly inexplicable in the traditional semantic frameworks (a la Montague or Kamp), since the computation of semantic representations consists in retrieving information stored in the lexicon and combining them according to the syntactic structures. A detailed study of the French definite article convincd us that they involve instructions to process contextual information. They trigger off a search in the knowledge base, the purpose of which is to identify a referent. If the procedure succeeds and returns a constant, definite articles acquire a logical representation in the spirit of Russell. Thus we have the means of reconciling the logical approach of Russell and the pragmatic approach of Hawkins (1977). This article consists of three parts: first, we introduce our linguistic model; second, we give a sketch of a system of rules to parse some of the French determiners; third, we give a thorough study of the definite article le.