Contrastive Accent in a Data-to-Speech System

Being able to predict the placement of con-trastive accent is essential for the assignment of correct accentuation patterns in spoken language generation. I discuss two approaches to the generation of contrastive accent and propose an alternative method that is feasible and computationally attractive in data-to-speech systems. 1 Motivation The placement of pitch accent plays an important role in the interpretation of spoken messages. Utter-antes having the same surface structure but a different accentuation pattern may express very different meanings. A generation system for spoken language should therefore be able to produce appropriate ac-centuation patterns for its output messages. One of the factors determining accentuation is contrast. Its importance canbe illustrated with all example from GoalGetter, a data-to-speech sys-teln which generates spoken soccer reports in Dutch (Klabbers et al., 1997). The input of the system is a typed data structure containing data on a soccer match. So-called syntactic templates (van Deemter and Odijk, 1995) are used to express parts of this data structure. In GoalGetter, only 'new' information is accented; 'given' ('old') information is not However, this strategy does not always lead to a correct accentuation pattern if contrastive information is not taken into account, as shown in example (1). t (1) a Ill the 16th minute, the Ajax player Kluivert kicked the ball into the wrong goal. b Ten minutes later, Wooter scored for Ajax. 1 All GoalGetter examples are translated from Dutch. Accented words are given in italics; deaccented words are underlined. This is only done where relevant. The word Ajax in (1)b is not accented by the system , because it is mentioned for the second time and therefore regarded as 'given'. However, this lack of accent creates the impression that Kluivert scored for Ajax too, whereas in fact he scored for the opposing team through an own goal. This undesirable effect could be avoided by accenting the second occurrence of Ajax in spite of its givenness, to indicate that it constitutes contrastive information. 2 Predicting contrastive accent In this section I discuss two approaches to predicting contrastive accent, which were put forward by Scott Prevost (1995) and Stephen Pulinan (1997). In the theory of contrast proposed in (Prevost, 1995), an item receives contrastive accent if it co-occurs with another item that belongs to its 'set of alternatives', i.e. a set of different items of the same type. There are two main problems with this approach. First, as …