Heroes, villians, magicians, …

One difficulty in creating synthetic characters for interactive stories is that these characters must convey their role in the story in a believable way. However, the relation between believability, on one side, and the role a character plays in a drama, on the other, has not yet been fully addressed. In this paper we will present a view on how to develop believable synthetic characters whose behaviour is based on a set of predefined functions (Propp's functions) associated with the role they play in the story. To illustrate the approach, we will present a collaborative virtual environment, Teatrix, designed for children to build their own stories-fairy tales. In Teatrix, virtual actors play roles (such as villain, hero, magician, etc), which are functional for the development of the story. Such roles have pre-defined goals and plans, allowing the story to flow and climax situations to arise. Teatrixis already in use by children ages between 7 and 9, in the context of a Computer-Integrated Classroom scenario.