Representing Knowledge for Planning Multisentential Text

The AlethGen tool has been used to build a system for automatically generating replies to complaints, for a European mail-order company. In the current version, letters are generated in French. AlethGen consists of several modules: the text deep structure planner (or conceptual planner), the text surface structure planner (or rhetorical planner), the computation of pronouns and quantifiers, and the linguistic generator proper (globally inspired by the Meaning-Text Theory) which determines the concrete realization of sentences. The paper mainly describes Ale thGen 's conceptual and rhetorical planners and focuses on the knowledge they use and produce. 1. Goals and general approach The main function of the texts we had to generate consisted indeed in replying to a complaint, thus in arguing and justifying a decision. This implies, on the one hand, a good management of the argumentative aspects, and on the other hand, the need to generate rather complex texts in a perfectly consistent style. The general approach of the conceptual planning is relation-based, as described in the Rhetorical Structure Theory or RST (Mann & Thompson, 1988). However, as shown in (Elhadad & Mc Keown, 1990), previous works in text generation systems (including RST) "have generally used a notion similar to rhetorical relations to descr ibe the connect ion between propositions. They make a one-to-one mapping from these relations to connectives for generation (for example, the "opposition" relation would be realized by the connective "but"). In this approach it is difficult to distinguish between similar connectives (e.g. [...] but vs. although)." In our work, we assume that there are two different levels of text structure. The deep level is represented by unordered basic relations, and the surface level is represented by (ordered) lists of atomic events and rhetorical operators.