Interactive storytelling systems have become very popular
as they engage users in the creation of narrative. In order to explore a co-creation process where the final result is narrated while the user is playing, we have designed an interactive storytelling system that is able to generate a narration in real time while giving the user the possibility to decide what to do and where to go. The intended result is a tool that allows the author, the user and the system to co-create a narration giving the user, as the ultimate author of the resulting narration, the freedom to decide the course of the events. In this paper we focus on the structures that have been used to represent the stories and in the mechanisms designed to generate the narration so that a coherent and entertaining story can be presented to the user.