The facts of our knowledge base are interconnected in various ways, and to facilitate content selection and structuring, we organise the facts into a text potential -- a graph of facts interconnected in terms of thematic and rhetorical relations. The text potential is an intermediary stage between the knowledge base and text, motivated in a similar way to DRSs [Kamp 81] by the desire explicitly to represent the selection of possible knowledge structures that can be reflected linguistically. Most of the text potential is precompiled, though some aspects of the text potential change dynamically and have to be computed on demand.
As Figure 1 shows, the text potential forms a three-tiered structure of entities, facts and relations. There are links between items in adjoining tiers, but no links within a tier or between entities and relations. We now discuss the three tiers in turn.
