Descriptional Anaphora In Discourse Representation Theory

Standard Discourse Representation Theory (DRT) was designed mainly to explain the so-called donkey-sentences. The pronouns plaYing such a prominent role in all these sentences belong, however, exclusively to one (partlculaPly simple) type of pronoun. We try to extend DRT in order to cover an equally Important type of pronoun, the so-called etdes0rIptlonal,* pronoun. Discourse referents ape now used Eo carry information o n the intenslon of their referents as well as on the extenslon. This allows, at the same time. to suggest accessibility rules for Pronouns which are more appropriate than those suggested by traditional DRT. These new rules ape based on the generlcness of the sentences involved. 1. PRONOMINAL REFERENCE AS STARTING POINT fOR DISCOURSE REPRESENTATION THEORY One of the starting points fop the development of DRT in Kamp*s orlglnal paper (Kemp 1981) was the seemingly erratic behaviour shown by indefinite noun phrases under a traditional logical analysis, a n d the equally erratic interactions that seem to obtain between Indeflnire noun phrases and inter-sententlal and intPa-sententlal PPonomlnal references to them. Of PartlculaP Interes~ was the behaviour of indefinite noun phrases in the so-called donkey-sentences. 1.1 D e f i n i t e n e s s and I n d e f i n i t e n e s s in T r a d i t i o n a l L i n g u i s t i c Theory The traditional, and intuitively quite convincing, view has it that definite noun phrases refer to an object that is already familiar to the speaker (and possibly also to the listener), whereas indefinite noun phrases introduce new objects. This theory looks convincing as lone as we consider explicit deflnites, as in 1) John owns a donkey. John bea ts the Oonkey where the donkey is introduced as exlstln s by the indefinite noun phrase and referred to as familiar by the following definite noun phrase. Personal pronouns are, under the accepted Interpretation, contracted forms of definite noun phrases, and the familiarity hypothesis often works reasonably well fop them. too: In the following paraphrase of i: 2) John owns a donkey. He bea ts i t the definite pronoun refers to the donkey which is familiar after it has been Introduced by an indefinite noun phrase, and the definite pronoun is. in other words. co-referentlal with the pPecedlng Indeflnire noun Phrase. For this reason the traditional interpretation of noun phrases a n d pronouns is called "referential". But problems surface if we consider sentences such as 3) John d o e s n ' t own a donkey 4) Every boy l i k e s h i s mother Neither does the indefinite noun phrase in 3 assert that there is a donkey that John owns, nor can we really say that the pronoun "his" in ~ refers to something familiar. Indeed. we can hardly se.v that it refers to anything at all: If we stick to the traditional view of what reference is, viz. a relationship between an expression of language and a real object, then there can be no reference at all in ~, since no existence of any boys was ever asserted. It was examples such as those that brought t h e whole familiarity theory into disrepute (of. the s h o r t historical outline given by Helm 1983). 1.2 D e f i n i t e n e s s and I n d e f i n i t e n e s s i n L o g i c a l l 7 Or ien ted L i n g u i s t i c s One radical solution to the problem of non-referring noun phrases was suggested by Russell in his classical Theory of Descriptions. Zn it. both definite and indefinite articles are interpreted as existential quantlflers (with the addl-