Performing aggregation and ellipsis using discourse structures

This article describes the generation of aggregated and elliptic sentences, using Dependency Trees connected by rhetorical relations as input. The system we have developed can generate both hypotactic and paratactic constructions with appropriate cue words, and various forms of ellipsis such as Gapping and Conjunction Reduction. We contend that Dependency Trees connected by rhetorical relations are excellent input for a generation system that has to generate ellipsis, and we propose a taxonomy of the most common Dutch cue words, grouped according to the kind of discourse relations they signal. Finally, we argue that syntactic aggregation should be performed in the Surface Realizer of a language generation system, because it requires access to language-specific syntactic information.