A Logical Formalism for the Representation of Determiners

A LOGICAL FORMALISM FOR THE REPRESENTATION OF DETERMINERS f Barbara Di Eugenio~ Leonardo Lesmo, Paolo Pogliano, Pietro Torasso, Francesco Urbano Dipartimento di Informatica - Universita' di Torino Via Valperga Caluso 37 ~ 10125 Torino ~ Italy ABSTRACT Determiners play an important role in conveying the meaning of an utterance, but they have often been disregarded, perhaps because it seemed more i~portant to devise methods to grasp the global meaning of a sentence, even if not in a precise way. Another problem with determiners is their inherent a~bigulty. In this paper we propose a logical formaliem, which, among other things, is suitable fc~ representing determiners without forcing a particular interpretation when their meaning is still not clear. INTRODUCTION Ambiguity of determiners is one of the most striking phenomena of natural language; what is strange is the case with ~hich humans use them: it seems that the molteplicity of interpretations of a ncun phrase including a determiner is not explicitly perceived by human users of rmtural language [Hobbs 1983]. The approach we chose tries to model this behavier: each determiner has a charac ~ teristic semantic interpretation, which is different from that of ot]qer determiners and which can be furtherly specified an the basis of the information contents gathered from the overall ean ~ text and frfxn the remsining part of the sentence. If such an information contents is rot sufficient, then the meaning of the determiner remains ambiguous. What is of paramount i~rtance is that any determiner has a "single" meaning, that can be furtherly specified by the context. Of course, we need to express the se~sntics of determiners by means of a suitable representation. The one that we propose seems to be intuitively acceptable, formally precise and suitable for a cm~positional analysis of natural language that, even if questien - able in some particular cases, is still one of the approaches that guarantee the most reasonable degree of generality in semantic interpretation. It is obvious that the representation of a sentence in such a fon~sliem may contain ambiguities; therefore a further step is needed in order to obtain an unambigtmus deep specification of its meaning. Contrarily to the intermediate logical formalism we are going to discuss, this firml specification will rot be given in declarative form, but in terms of operations on an underlying knowledge base. REPRESENTATION FORMALISM Ct~ main goals in designing the representation formalism that will be used in the following sections were: I ) To maintain a close relationship between the pieces of informs- tion that are intuitively present in the input sentence and the predicates appearing in its interpretation. 2) To make explicit the distinction between surface objects and semantic entities: words on one side and concepts, individuals, classes etc. on the other. 3) To maintain a co~itional analysis of language, where the starting point is provided by the dependency tree built by the rule~bassd syntactic cogent of the FIDO system [Le~no, Torasso 84; Les~o, Torasso 85a; Lesmo, Toraseo 85b]. + Partially supported by MPI Project …

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