Optimising referential coherence in text generation

This paper describes an implemented system which uses centering theory for planning of co-herent texts and choice of referring expressions. We argue that text and sentence planning need to be driven in part by the goal of maintaining referential continuity and thereby facilitating pro-noun resolution: obtaining a favourable ordering of clauses, and of arguments within clauses, is likely to increase opportunities for non-ambiguous pronoun use. Centering theory provides the basis for such an integrated approach. Generating coherent texts according to centering theory is treated as a constraint satisfaction problem. We report on two empirical studies: a paired-comparison experiment to test whether readers prefer texts that adhere to centering constraints, and what we believe to be a novel method of corpus analysis involving perturbances, to investi-gate whether authors aim to promote referential coherence and if so, which centering constraints are more important.