Abstract. During the fast evolution of automatic direction of Interactive Digital Storytelling many description of similar ideas have appeared in the academic literature. System architectures and workflows are usually presented using informal descriptions and diagrams, what makes difficult to identify what are the real contributions of each publication. In the way of establishing a safe ground for future research on this topic, this paper is a first step towards the formalization of a particular paradigm for developing automatic storytellers. The chosen paradigm is RolePlaying Game Mastering, which computational model is presented using UML.