In this contribution, “Interactive Digital Storytelling” is viewed as a hybrid form of game design and cinematic storytelling for the understanding and creation of future learning and entertainment applications. The result of several practical experiments in the design of interactive agents for storytelling, a formal design model is presented that provides a conceptual bridge between both traditional linear narrative techniques, as well as emergent conversations with virtual characters. This model describes several levels of apparent semi-autonomy in an agent-based artefact and agency experienced by participants, which draw - in the broadest sense from Aristotle’s elements of structure in drama. In summary, thinking models for several design levels of interactive narrative are pictured from a creator’s point of view. Keywords interactive storytelling, digital storytelling, storytelling agents, story simulation