Using Cue Phrases to Determine a Set of Rhetorical Relations

based' approaches to discourse analysis and text generation suuer from a common problem: there is considerable disagreement between researchers over the set of relations which is proposed. Few researchers use identical sets of relations, and many use relations not found in any other sets. This proliferation of relations has been pointed out before (eg Hovy 1]), and several methods for justifying a standard set of relations have been proposed: this paper reviews some of these, and presents a new method of justiication which overcomes some awkward problems. Descriptive Adequacy Clearly, a set of relations must havègood coverage'|it must be possible to analyse all the texts of the kind targeted using the speciied relations. At the same time, this cannot be the only requirement on a set of relations, because many diierent sets of relations can be used to describe the same set of texts. For instance, the level of detail of the description is not constrained: how do we decide whether or not to subdivide result into volitional result and non-volitional result? Again, diierent cuts through the space of relations are possible: why distinguish between volitional and non-volitional result, and not between, say, immediate and delayed result? In fact the notion of`descriptive adequacy' seems to make little sense in isolation: in addition, it is necessary to specify a purpose for which the proposed description is adequate. Psychological Reality One way that a purpose can be speciied is by stipulating that relations modeìcognitive' constructs|that is, constructs which people actually use when they create and interpret text. On this conception, a description of the relations in a text becomes part of a theory of how the text originated, and why it is the way it is. This stipulation gives relations real explanatory power in a theory of discourse coherence: we could argue that it is because a