A Survey on Story Generation Techniques for Authoring Computational Narratives <s> II. TERMINOLOGY <s> A drama manager (DM) monitors an interactive experience, such as a computer game, and intervenes to shape the global experience so that it satisfies the author's expressive goals without decreasing a player's interactive agency. Most research on drama management has proposed AI architectures and provided abstract evaluations of their effectiveness; a smaller body of work has also evaluated the effect of drama management on player experience. Little attention has been paid, however, to evaluating the authorial leverage provided by a drama-management architecture: determining, for a given architecture, the additional non-linear story complexity a drama manager affords over traditional scripting methods. In this paper, we propose three criteria for evaluating the authorial leverage of a DM: 1) the script-and-trigger complexity of the DM story policy; 2) the degree of policy change given changes to story elements; and 3) the average story branching factor for DM policies versus script-and-trigger policies for stories of equivalent quality. We apply these criteria to declarative optimization-based drama management (DODM) by using decision tree learning to capture equivalent trigger logic, and show that DODM does in fact provide authorial leverage. <s> BIB001 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> II. TERMINOLOGY <s> As the domain of Interactive Digital Narrative matures, it becomes increasingly important for researchers to understand the conceptual differences and underlying theories in the different approaches. This paper presents new theoretical perspectives on the fragmented theory and practice within the domain and proposes first steps towards a unified theoretical framework for the domain. The paper is informed by the discussions between theorists and practitioners at two workshops held by the authors. <s> BIB002
In this section, we discuss the terminology used throughout the survey and present our categorization of the field of narrative generation. We use the term computational narrative to refer to any form of narrative, which occurs as the result of a collaboration between one or more human authors and a computer, and, if applicable, we use authoring tool to refer to any software which is used. We define the author as being the individual who provides content during the authoring process, be it for plot, space, constraints, images, etc. In the case of interactive narratives, we explicitly distinguish the narrative, which is authored in advanced, and an instantiated narrative, which is the particular narrative experienced by a particular individual while interacting with the system. This separation is based upon the distinction used by Koenitz et al. BIB002 . We will use the term interactor for this individual and resist any strict definition as the interactor may take on a number of roles, such as being a coauthor and contributing parts of the instantiated narrative, being an actor and taking the role of one of the characters, or simply observing a story as it unfolds. Furthermore, we restrict the work discussed in this survey to systems and tools which explicitly state their storytelling intent. We define narrative generation as the field of research concerned with the automatic generation of narrative. We define degree of automation as the extent to which an authoring task is automatically performed by a computer. This can range between a task completely performed by the computer, an automatic task, and one which must be performed entirely by the human, a manual task. Chen et al. formally define the term authorial leverage as being a measure of the variety and complexity of plots which may be created inversely to the authorial burden it places on the human author BIB001 . In this sense, higher authorial leverage relates directly to our concept of automation, where an increasing amount of work is done by the computer, in order to reduce the burden placed on the human author.