Situations and Prepositional Phrases

SITUATIONS AND PREPOSITIONAL PHRASES Erik Colban and Jens Erik Fenstad University of Oslo Institute of Mathematics Postboks 1053 Blindern N-0316 Oslo 3, Norway ABSTRACT This paper presents a format for representing the linguistic form of utterances, called situation schemata, which is rooted in the situation semantics of Barwise and Perry. A treatment of locative prepositional phrases is given, thus illustrating the generation of the situation schemata and their interpretation in situation semantics. Introduction A natural language system aims to provide an overall framework for relating the linguistic form of utterances and their semantic interpretation. And the relation between the two must be algorithmic. In this paper we pursue an approach which is based on an algorithm for converting linguistic form to a format which we call a situation schema. A situation schema has a well-def'med formal structure, suggestive of logical form. This is a structure which is different from the standard model- theoretic one; we will argue that it is a structure better adapted for the analysis of the meaning relation in natural languages. A situation schema is effectively calculable from the linguistic form and we believe that it provides a format usefull for further processing, e.g. in the construction of a natural language interface with a data system and also in connection with mechanical translation systems. The general structure of situation schemata We begin by explaining the general structure of the situation schemata and how they, are rooted in the situation semantics of Barwise and Perry (Barwise and Perry 83). Situation semantics is grounded in a set of prinutives S situations R relations L locations D individuals The format of a bas/c (located)fact is at I: r, al,...,an; 1 at 1: r, al ..... an; 0, the first expresses that at the location 1 in L the relation r in R holds of the individuals al ..... an in D; the second expresses that it does not hold. A s/mat/an s in S determines a set of facts of the form in s:at l:r, al ..... an; 1 or in s:at l:r, al ..... an; 0. We can think of a situation s as a kind of restricted, partial model (data base) which classifies certain basic facts. The set of primitives <S,L,R,D> may come with some internal structure, e.g. the set L of locations is or represents connected regions of space time and thus could be endowed with a rich geometric structure. We shall see how this can be exploited in our analysis of locative prepositional phrases. A situaion schema is a complex feature-value structure computable from the linguistic form of the utterance and with a choise of features matching the primitives of situation semantics: "REL ARG1 - AEEm - LOC .POL - Here the features REL ARG1,...,ARGn, arid LOC correspond to the primitives: relation, individuals, 258 location. POL, abbreviating polarity, takes either the value 1 or 0. The values in the schemata can either be atomic or complex feature-value structures. The value of the LOC feature is always …

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