A Survey on Story Generation Techniques for Authoring Computational Narratives <s> A. Space Generation and Computational Narrative <s> TALE-SPIN, the last major AI attempt at story generation, approached the problem of making up atoriea primarily from the perspective of an impartial world simulator. AUTHOR is a program (under development) which generates atoriea as a creative reasoner in pursuit of her own narrative goals. It is thus intended to simulate an author's mind as ahe makes up a story, rather than the world as things happen in it. The four major forces driving the story generation process, according to the AUTHOR model, are (1) author intentionality, (2) conceptual reformulation, (3) reminding, and (4) the opportunity enhancement metagoal. <s> BIB001 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> A. Space Generation and Computational Narrative <s> This paper describes an approach for managing the interaction of human users with computer-controlled agents in an interactive narrative-oriented virtual environment. In these kinds of systems, the freedom of the user to perform whatever action she desires must be balanced with the preservation of the storyline used to control the system's characters. We describe a technique, narrative mediation, that exploits a plan-based model of narrative structure to manage and respond to users' actions inside a virtual world. We define two general classes of response to situations where users execute actions that interfere with story structure: accommodation and intervention. Finally, we specify an architecture that uses these definitions to monitor and automatically characterize user actions, and to compute and implement responses to unanticipated activity. The approach effectively integrates user action and system response into the unfolding narrative, providing for the balance between a user's sense of control within the story world and the user's sense of coherence of the overall narrative. <s> BIB002 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> A. Space Generation and Computational Narrative <s> As a game designer or new media storyteller, you know that the story is everything. However, figuring out how to tell it interactively-and in a way that keeps your audience coming back for more-can be challenging. Here to help you out (and to open your mind to ever more creative ways of producing those stories) is the man who created the cult publication The Art of Computer Game Design and who has devoted much of his career to that very topic: Chris Crawford. To highlight the path for future gains in the quest for a truly interactive story, Chris provides a solid sampling of what doesn't work, contrasting unsuccessful methodologies with those that hold promise for the future. Throughout you'll find examples of contemporary games that rely on different technologies-and learn the storytelling lessons to be garnered from each of the past methodologies. Within the context of interactive storytelling, Chris explores ways of providing conflict and challenge, the difference between low- and high-interactivity designs, the necessity to move beyond purely visual thinking (so that the player is engaged on multiple levels), and more. <s> BIB003 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> A. Space Generation and Computational Narrative <s> The ability to generate narrative is of importance to computer systems that wish to use story effectively for entertainment, training, or education. One way to generate narrative is to use planning. However, story planners are limited by the fact that they can only operate on the story world provided, which impacts the ability of the planner to find a solution story plan and the quality and structure of the story plan if one is found. We present a planning algorithm for story generation that can nondeterministically make decisions about the description of the initial story world state in a least-commitment fashion. <s> BIB004 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> A. Space Generation and Computational Narrative <s> In interactive plan-based narrative environments, users' actions must be monitored to ensure that conditions necessary for the execution of narrative plans are not compromised. In the Zocalo system, management of user actions has been performed on a reactionary basis by a process called mediation. In this paper, we describe an extension to this approach, proactive mediation, which calculates responses to user input in an anticipatory manner. A proactive mediation module accepts as input a plan describing the actions being performed by the user (generated by a plan recognition system) and identifies portions of that plan that jeopardize the causal structure of the overall narrative. Once these portions are identified, proactive mediation generates modifications to the narrative plan structure that avoid the unwanted interaction between user and story. This extension to the original mediation algorithm provides more responses to a user's actions and generates responses that are tailored to the user's activity. <s> BIB005 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> A. Space Generation and Computational Narrative <s> In this paper we present our continuing efforts to generate narrative using a character-centric approach. In particular we discuss the advantages of explicitly representing the emergent event sequence in order to be able to exert influence on it and generate stories that ‘retell' the emergent narrative. Based on a narrative distinction between fabula, plot and presentation, we make a first step by presenting a model based on story comprehension that can capture the fabula, and show how it can be used for the automatic creation of stories. <s> BIB006
In his survey on creativity and computational storytelling, Gervás identified two approaches to story generation  . The first involved generating the plot from the space, as evidenced, e.g., with TALE-SPIN  . For the second approach, he discussed Dehn's AUTHOR BIB001 , a proposal for a story generation tool wherein the construction of the space would be automated according to the plot. TALE-SPIN relied on character goals, whereas AUTHOR relied on authorial goals. Character goals refer to the goals set by virtual agents inhabiting the space, while authorial goals refer to the intended story (or story components) of the author using the generation system. While both character and authorial goals have been used for plot generation, one would expect that space generation would be of use either to assist characters in meeting their goals, or to better realize the intended vision of the author. While the former was explored by Swartjes et al.  , in practice, authorial goals have been more closely viewed as constraints, particular plot events, or structures which must be obeyed by the plot generators. In that sense, most plot generators have concentrated on guiding events to reach the author's intended goals, relying on minimal or no space generation. In traditional stories, space generation may amount to FABULIST's goal of dynamically generating space based on indeterminate information BIB004 . In interactive games, this amounts to modifying the space in order to block unwanted interactor actions using a form of narrative mediation, either by changing space as a reaction to a deviation, for example causing the interactor's gun to jam if they are going to shoot an important character BIB002 , or by proactively making changes in the space to render some potential plot deviations impossible BIB005 . Emergent systems, on the other hand, may automate plot and space entirely, but may include some form of story or drama manager to form the character actions into some form of coherent plot BIB006 . It seems, however, that these methods are not quite in line with Dehn's original argument, that the space of the story is built to suit the plot. As stated by Dehn, the "storyworlds [spaces] are developed by authors as needed, often as post hoc justification for events that the author has already decided she wants as part of the story" BIB001 . We discussed several systems more closely related to this concept in Sections V and VI. However, most only make minor changes to the space or are considered distinctly separate to the computational storytelling community. Thus, in the majority of systems from within the storytelling community, the burden is on the author to create a space. Furthermore, the quality of this space often directly relates to the quality of the story BIB004 ,  , BIB003 . This challenges Lubart's original intention of the computer as a collaborator, in that the success of the generation technique is still entirely dependent on a high-quality manually authored space. By categorizing all of the major systems and techniques discussed, as shown in Table I , we can distinctly see a number of gaps relating to different combinations of plot and space generation. One interesting direction would involve exploring the space generation for plot templates. Since these templates leave open roles, a space generator would have more freedom to generate unique content with a greater reduction in terms of plot limitations. For example, it could present the author with a number of automatically created existents for each of the roles, which the author could then select from. It would also be of interest to explore the notion of fully automatic space generation, into which none of the systems surveyed could be categorized. 