Generating Referring Expressions Involving Relations

Generating Referring Expressions Involving Relations Robert Dale Department of Artificial Intelligence and Centre for Cognitive Science University of Edinburgh Edinburgh EH8 9LW Scotland R. Dale~uk. ac. edinburgh Abstract In this paper, we review Dale's [1989] algorithm for determining the content of a referring expres- sion. The algorithm, which only permits the use of one-place predicates, is revised and extended to deal with n-ary predicates. We investigate the problem of blocking 'recursion' in complex noun phrases and propose a solution in the context of our algorithm. Introduction In very simple language generation systems, there is typically a one-to-one relationship between en- tities known to the system and the linguistic forms available for describing those entities; in effect, each entity has a canonical name. In such sys- tems, deciding upon the form of reference required in a given context requires at most choosing be- twc(,n a pronoun and the canonical name. 1 As soon as a generation system has access to a knowledge base which contains richer knowledge about the entities in the domain, the system has to face the problem of deciding what particular properties of an entity should be used in describ- ing it in a given context? Producing a descrip- tion which includes all of the known properties of Lhe entity is likely to be both inefficient and t~.Ve do not mean to imply, of course, that the de- cision as to whether or not to use a pronoun is simple. 2This problem exists quite independently of any considerations of the different perspectives that might be taken upon an entity, where, for examplep one entity can be viewed from the perspective of be- ing a father, a bicyclist and a teacher, with separate clusters of properties in each case. Even if the system is restricted to a single perspective upon each entity (as almost all language generation systems are), in any sophisticated knowledge base there will still be more information available about the entity than it is sen- sible to include in a description. Nicholas Haddock Hewlett Packard Laboratories Filton Road Stoke Gifford Bristol Bsl2 6QZ England njh@com, hp. hpl. hplb misleading. The core of the problem is finding a way of de- scribing the intended referent that distinguishes it from other potential referents with which it might be confused. We refer to this problem as the content determination task. In this paper, we point out some limitations in an earlier solu- tion proposed in Dale [1988, 1989], and discuss the possibilites of extending this solution by in- corporating a use of constraints motivated by the work of Haddock [1987, 1988]. Generating Referring Expressions The Principles of Reference Dale [1988, 1989] presents a solution to the con- tent determination task which is motivated by three principles of refcrence. These are cssen- tinily Gricean conversational maxims rephrased from the perspective of generating referring ex- pressions: 1. The principle of sensitivity states that the referring expression chosen should take account of the state af the hearer's knowledge. 2. The principle of …

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