A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Abstract The generation of extended plots for melodramatic fiction is an interesting task for Artificial Intelligence research, one that requires the application of generalization techniques to carry out fully. UNIVERSE is a story-telling program that uses plan-like units, ‘plot fragments’, to generate plot outlines. By using a rich library of plot fragments and a well-developed set of characters, UNIVERSE can create a wide range of plot outlines. In this paper we illustrate how UNIVERSE's plot fragment library is used to create plot outlines and how it might be automatically extended using explanation-based generalization methods. Our methods are based on analysis of a television melodrama, including comparisons of similar stories. <s> BIB001 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> One way of characterising texts is in terms of the discourse structures on which they appear to be built. Each type of text, or genre, e.g. the sports report, the recipe, the sermon, the proverb, will have associated with it a characteristic organisation of units. In this paper, a general model of the structure of one text type, the story, is described. This model forms the basis of a program which combines the general story structure principles with rules governing a particular sub-genre, the Old French epic, in order to generate story summaries. <s> BIB002 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Abstract Interactive digital storytelling promises to be a new artistic discipline. But what does the artwork look like? And how much control does the artist have over the final result? By searching for the right answers, we draw several approaches from diverse fields such as filmmaking, game design, autonomous agents, psychology, and narrative intelligence. We first give a definition of interactive storytelling that includes a scope between authorship and emergent narrative, and present two example projects with different emphases. Then, we introduce a multi-level concept for an experimental stage that can be used to explore interactive storytelling at varying degrees of flexibility versus predetermination. Instead of inventing the ultimate virtual narrator, we suggest developing layers of run-time engines that allow authors to work with directions on each single layer separately—from selecting high-level dramatic structures down to directing animated actors. The concept of underlying models at each level is explained in detail by the example of a story model implementation. Further, we show variations of level adjustments causing graded degrees of semi-autonomy. First results of this experimental stage are presented, and the primary future tasks are pointed out. <s> BIB003 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> essence of the computer as a representational m edium is procedurality - the ability of the computer to enga ge in arbitrary mechanical processes to which observers can ascribe meaning. Taking full representational advantage of the compu ter thus requires procedurally literate authorship, that is, artists and writers who are able to think about and work within computational frameworks; in the extreme case of developing new modes of computational expression, authors must be highly pr oficient in the use of general purpose programming languages. We examine issues of procedural authorship using the interacti ve drama Facade as a case study. Facade's explicit design goal is to provide the player with local and global agency ove r the evolution of the dramatic experience; this requires a level o f procedurality previously not implemented in interactive narrative . of a process. In the extreme case of developing new modes of computational expression, authors must be highly pr oficient in the use of general purpose programming languages, used to construct new languages and tools specialized for the new rep resentational mode. In this paper we provide a case-study, using the in teractive drama Facade , of this last case of procedural authorship. Facade represents a new mode of computational representati on, interactive drama , combining the game-like pleasure of moment- by-moment interaction with believable characters, with the story- like pleasure of participating in and influencing a long-term dramatic progression. As procedural authors, we und ertook several design-plus-programming tasks: deconstructi ng a dramatic narrative into a hierarchy of story and behavior pi eces; designing an AI (artificial intelligence) architecture, and c ollection of special purposes languages within the architecture, that respond to and integrate the player's moment-by-moment interactions to reconstruct a real-time dramatic performance from t hose pieces; and writing an engaging, compelling story within th is new framework. This paper makes a case for the importance of proce dural authorship, describes the design goals of Facade and how these goals could only be met through a highly procedural approach to interactive narrative, and finally describes Facade's architecture, content organization, and the experience of authori ng within this framework. <s> BIB004 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> In recent years, the fields of Interactive Storytelling and Player Modelling have independently enjoyed increased interest in both academia and the computer games industry. The combination of these technologies, however, remains largely unexplored. In this paper, we present PaSSAGE (Player-Specific Stories via Automatically Generated Events), an interactive storytelling system that uses player modelling to automatically learn a model of the player's preferred style of play, and then uses that model to dynamically select the content of an interactive story. Results from a user study evaluating the entertainment value of adaptive stories created by our system as well as two fixed, pre-authored stories indicate that automatically adapting a story based on learned player preferences can increase the enjoyment of playing a computer role-playing game for certain types of players. <s> BIB005 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> This paper describes the Generator of Adaptive Dilemma-based Interactive Narratives (GADIN) system. This system automatically generates interactive narratives which are focused on dilemmas in order to create dramatic tension. The user interacts with the system by making decisions on relevant dilemmas and by freely choosing their own actions. In this paper we introduce the version of GADIN which is able to create a finite story. The narrative finishes - in a manner which is satisfying to the user - when a dynamically determined story goal is achieved. Satisfaction of this goal may involve the user acting in a way which changes the dispositions of other characters. If the user actions cause the goal to become impossible or unlikely then they cause the story goal to be re-selected, thus meaning that the user is able to fundamentally change the overall narrative while still experiencing a coherent narrative and clear ending. This method has been applied within the children's story domain of a dinosaur adventure but is applicable in any domain which makes use of cliched storylines. The story designer is required only to provide genre-specific storyworld knowledge and dilemmas. <s> BIB006 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Interactive storytelling (IS) systems are an emerging class of interactive entertainment applications with an emphasis on narrative aspects. One of the approaches used to develop IS applications is based on planning algorithms. This article describes two mechanisms that can be introduced to planning-based IS in order to solve two problems that are inherent in this approach. The first is a technique to control the pace at which a story evolves, so that the story that is generated follows a specific tension arc. The second is a method that makes it possible to avoid dead-ends in a story by intervening to justify previous events. These mechanisms help to produce a more enjoyable user experience, since their use tends to result in stories with higher narrative consistency. Results from experiments with users suggest that the proposed mechanisms improve both of the aspects addressed by this article. <s> BIB007 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Story Canvas is a visual authoring tool for the creation of interactive, generative stories. Aimed at authors without a technical background in computational storytelling, our system takes an existing author goal-based narrative planning architecture and adds a highly visual authoring and reading interface to the technology, using the language of storyboards and comics as a framework for both authoring and interacting with the resulting narratives. In this paper we describe Story Canvas and its evolution from our previous authoring work, including how our interface choices have been driven by our previous experiences with non-technical authors, and describe the details of translating the visual authoring constructs into story plans within the story generator. <s> BIB008 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> We have seen ten years of the application of AI planning to the problem of narrative generation in Interactive Storytelling (IS). In that time planning has emerged as the dominant technology and has featured in a number of prototype systems. Nevertheless key issues remain, such as how best to control the shape of the narrative that is generated (e.g., by using narrative control knowledge, i.e., knowledge about narrative features that enhance user experience) and also how best to provide support for real-time interactive performance in order to scale up to more realistic sized systems. Recent progress in planning technology has opened up new avenues for IS and we have developed a novel approach to narrative generation that builds on this. Our approach is to specify narrative control knowledge for a given story world using state trajectory constraints and then to treat these state constraints as landmarks and to use them to decompose narrative generation in order to address scalability issues and the goal of real-time performance in larger story domains. This approach to narrative generation is fully implemented in an interactive narrative based on the “Merchant of Venice.” The contribution of the work lies both in our novel use of state constraints to specify narrative control knowledge for interactive storytelling and also our development of an approach to narrative generation that exploits such constraints. In the article we show how the use of state constraints can provide a unified perspective on important problems faced in IS. <s> BIB009 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Recent progress in narrative generation techniques for Interactive Storytelling supports increasingly longer stories. Consequently, the exploration of such automatically generated narratives for testing or evaluation purposes becomes increasingly difficult due to the many variants, even for stories of a few minutes' length. In this paper, we introduce a hypermedia method that supports the real-time navigation of 3D interactive narratives from their timeline description. The core idea behind our method is that it fully preserves the dynamic nature of the interactive narrative, unlike any form of visual replay or summarising. We illustrate the approach on a fully-implemented interactive narrative and show how it supports the exploration of different generated narratives in a way that assists testing and evaluation. <s> BIB010 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Marlinspike is an interactive drama system. It produces a story by playing short pre-authored story components called scenes in response to the actions of a human player. Marlinspike selects the next scene to play so as to reincorporate—or narratively build upon—as much of the story-so-far as possible. In accordance with an Aristotelian definition of narrative unity, this reincorporation serves to make earlier events—particularly the player's actions— narratively necessary to the finished story. An evaluation with human players of Marlinspike's novel reincorporation feature produced mixed results. On the one hand, reincorporation does indeed produce internal story structures that are more unified and that include more of the players' significant actions. However, the players themselves did not report a correspondingly improved experience of either story quality or story-level agency. <s> BIB011 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> In this article we explore the means by which state-of-the-art knowledge on children counseling techniques can be combined with digital interactive narrative tools to facilitate communication with children during counseling sessions. The field of "narrative play therapy" could profit from the reconciliation between free-play and narratives afforded by interactive digital tools in order to promote children's engagement. We present a digital interactive narrative application integrated with a "step-by-step" guide to the counselor, which could be adapted to many different situations and contexts where an adult professional counselor (or therapists) needs to establish a trustful and efficient communication with children. Furthermore, the tool was specifically customized to pediatric audiology counseling. Our evaluation shows that the tool maintains the centrality of the child's perspective thanks to the emergent interactive storytelling process. At the same time the counselor is given the means for obtaining valuable information for guiding and structuring the therapeutic process. <s> BIB012 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Scenario-based training exemplifies the learning-by-doing approach to human performance improvement. In this paper, we enumerate the advantages of incorporating automated scenario generation technologies into the traditional scenario development pipeline. An automated scenario generator is a system that creates training scenarios from scratch, augmenting human authoring to rapidly develop new scenarios, providing a richer diversity of tailored training opportunities, and delivering training scenarios on demand. We introduce a combinatorial optimization approach to scenario generation to deliver the requisite diversity and quality of scenarios while tailoring the scenarios to a particular learner's needs and abilities. We propose a set of evaluation metrics appropriate to scenario generation technologies and present preliminary evidence for the suitability of our approach compared to other scenario generation approaches. <s> BIB013 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Interactive narrative is a form of digital interactive experience in which users create or influence a dramatic storyline through their actions. The goal of an interactive narrative system is to immerse the user in a virtual world such that he or she believes that they are an integral part of an unfolding story and that their actions can significantly alter the direction and/or outcome of the story.In this article we review the ways in which artificial intelligence can be brought to bear on the creation of interactive narrative systems. We lay out the landscape of about 20 years of interactive narrative research and explore the successes as well as open research questions pertaining to the novel use of computational narrative intelligence in the pursuit of entertainment, education, and training. <s> BIB014 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Using procedural narrative generation in video games provides a flexible way to extend game play and provide more depth to the game world at low cost to the developers. Current examples of narrative generation in commercial games, however, tend to be simplistic, resulting in repetitive and uninteresting stories. In this paper, we develop a system for narrative generation using a context-aware graph-rewriting framework. We use a graph representation of the game world to create narratives which reflect and modify the current world state. Using a novel set of metrics to evaluate narrative quality, we validate our approach by comparing our generated narratives to other procedurally generated stories, as well as to authored narratives from commercially successful and critically praised games. The results show that our narratives compare favorably to the authored narratives. Our metrics provide a new approach to narrative analysis, and our system provides a unique and practical approach to story generation. <s> BIB015 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> This paper describes our effort for a planning-based computational model of narrative generation that is designed to elicit surprise in the reader's mind, making use of two temporal narrative devices: flashback and foreshadowing. In our computational model, flashback provides a backstory to explain what causes a surprising outcome, while foreshadowing gives hints about the surprise before it occurs. Here, we present Prevoyant, a planning-based computational model of surprise arousal in narrative generation, and analyze the effectiveness of Prevoyant. The work here also presents a methodology to evaluate surprise in narrative generation using a planning-based approach based on the cognitive model of surprise causes. The results of the experiments that we conducted show strong support that Prevoyant effectively generates a discourse structure for surprise arousal in narrative. <s> BIB016 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Conflict is an essential element of interesting stories. In this paper, we operationalize a narratological definition of conflict and extend established narrative planning techniques to incorporate this definition. The conflict partial order causal link planning algorithm (CPOCL) allows narrative conflict to arise in a plan while maintaining causal soundness and character believability. We also define seven dimensions of conflict in terms of this algorithm's knowledge representation. The first three-participants, reason, and duration-are discrete values which answer the “who?” “why?” and “when?” questions, respectively. The last four-balance, directness, stakes, and resolution-are continuous values which describe important narrative properties that can be used to select conflicts based on the author's purpose. We also present the results of two empirical studies which validate our operationalizations of these narrative phenomena. Finally, we demonstrate the different kinds of stories which CPOCL can produce based on constraints on the seven dimensions. <s> BIB017 </s> A Survey on Story Generation Techniques for Authoring Computational Narratives <s> 1) Grammar-Based Plot Generators: <s> Versu is a text-based simulationist interactive drama. Because it uses autonomous agents, the drama is highly replayable: you can play the same story from multiple perspectives, or assign different characters to the various roles. The architecture relies on the notion of a social practice to achieve coordination between the independent autonomous agents. A social practice describes a recurring social situation, and is a successor to the Schankian script. Social practices are implemented as reactive joint plans, providing affordances to the agents who participate in them. The practices never control the agents directly; they merely provide suggestions. It is always the individual agent who decides what to do, using utility-based reactive action selection. <s> BIB018
By linking a plot grammar to a space, it becomes possible to generate complete stories. In these generators, the plot grammar often contains authored rules that determine which existents may be linked to which events. Pemberton's GESTER is a plot generator which relies on a detailed plot grammar of Old French epic narratives BIB002 . Its grammar is divided both into specific events with causes and effects, but also a set of rules which defines the relations between existents in the space. Pemberton's approach is unique to many of the previous grammars in that these relations would influence the plot generation, closely linking space and plot. BRUTUS used plot grammars among many other formalizations of narrative for its construction of betrayal narratives  . BRUTUS was considerably successful in creating complex stories, but was geared specifically toward the generation of betrayal plots, limiting its potential as a generative system, but further highlighting the complexity which arises from moving from general descriptions of narrative and simple folktales to generating fully realized narratives. TEATRIX  is an interactive narrative system which used Propp's grammar to create templates based upon the folktale functions. In TEATRIX, both the author and the interactor are responsible for authoring content, with the author manually creating the templates and initial state of the space, and the interactor being able to select which existents will appear in the story, and which actions the different characters will take. The computer serves two roles in generating plot content, by automatically selecting the next plot template based on both the choices made by the interactor and the rules of Propp's grammar, and is also capable of automatically simulating character actions for characters not controlled by the interactor. GEIST BIB003 again uses Propp's grammar to procedurally create templates for interactive stories. The stories are unique in that they are represented in augmented reality and meant for tourists visiting new cities. Events in the plot occur at different locations in the real world, allowing the tourist to experience the story, while also visiting real-world locations and learning more about the history of the city they are visiting. GEIST's space is unique in that it is divided between the manually authored characters in the story, and also the real-world location which is intended to be the backdrop of the story. SQUEGE  utilizes a manually authored space and a grammar of plot structures. It uses rewrite rules to progressively build more complex plot structures, selecting characters or items arbitrarily from the space to fill certain roles in the plot. REGEN BIB015 takes the concept of using a grammar coupled with graph rewriting rules, but extends it to account for relationships between characters in the game world, and how these relations change due to events in the plot. For this, REGEN loosely examines the use of character goals for guiding plot generation, where the plots are created according a simulated model of characters and their relations. 2) Planning-Based Plot Generation: A popular approach for plot generation in the storytelling AI research community is using planning-based plot generation. The basic concept behind planning-based plot generation is that the generation process should yield a story that achieves a provided goal. This goal may take many forms and is often represented as a a desired state of one or more existents (e.g., relations, attributes, etc.) within the story space, and it is not uncommon for a system to have multiple goals, subgoals, or even changing goals. While there are many different types of goals, it is most common to either have the goals be provided by the author as a way enforcing that their intentions, or to have the goals be assigned to specific characters in the space. There will be many examples of planning-based plot generation throughout this survey, and in the following section, we only present those which do not automate space. UNIVERSE BIB001 is an early planning-based plot system and specifically aims at generating "soap-opera" styled plots. Planning is used to generate events which aim to cause melodramatic conflicts between characters. The modeling of character emotions is often considered important in the plot generation community BIB014 , since it provides useful details which can improve the emotional impact of the plot. This is especially important within dramatic plot generators, such as UNIVERSE, and allows the generators to move away from the heavily stereotyped roles seen in the folktale grammars. UNIVERSE uses an emotional model with several simple rankings on elements such as wealth, moodiness, and intelligence, as well as a set of character goals and even stereotypes, such as socialite or party-goer. These traits can act as constraints for certain events, for example, the author may state that only characters with a low niceness and high promiscuity may engage in affairs with other characters. UNIVERSE was also important in that it intended to run indefinitely, consistently creating new plot twists to keep in tune with the long-running soap-opera television series which inspired it. This was achieved by having the author create a number of plot fragments, each with its own goal, as well as an overall goal for the plot itself. By mixing and combining different fragments, new plots could be continuously created. Barber and Kudenko's GADIN BIB006 provided a similar "soapopera" oriented system, but one which allowed for interactivity, letting the interactor act as a character within the virtual soapopera rules. In such a way, the interactor also makes changes and guides the creation of a final instantiated story. STORY CANVAS BIB008 uses a similar planning technique to UNIVERSE and presents itself as a novice authoring tool for interactive stories. In STORY CANVAS, the author creates their goals as well as the rules for plot generation at a high level using hierarchical task networks. These are automatically converted into behavior scripts for each of the existents in the story. The space is also manually authored, using visual storyboards to select characters and set the relations between them. Porteous et al. used planning to adapt as a means to adapt the story dynamically to account for actions taken by the interactor BIB009 . The system presented an interactive version of Shakespeare's Merchant of Venice and planning was used to account for the potential player deviations from the original plot. The system worked by decomposing the original plot into a sequence of constraints on the story space and then using planning to iteratively build the plot. Replanning occurs whenever the interactor modifies the story space through some form of interaction. The interactor is further provided the option of viewing the plot from different points of view, in which the planner emphasizes certain events in the plot to allow for interpretations about different characters, for example, by emphasizing discriminatory events against one character to position them as a victim. Constraining the plot is interesting for interactive stories, in that the author is able to create a specific experience, but the automation of the computer allows for the interactor to further explore and influence the space without the concerns of ever deviating too far from the intended plot. A later version of the same system BIB010 provides an interesting mixed-initiative approach for authoring, where authors are able to scroll through their plot via a time-line and change specific plot events. The plot is then updated accordingly, and the author can cycle through later events in the plot to see how they have been modified. Plot constraint techniques have also been used to author plots for serious games, where the interactor is expected to experience a fixed scenario, but have the ability to view the scenario from different perspectives based on their actions  . While Porteous et al. were interested in constraining planning to accommodate particular plot events, Barros and Musse's FABULATOR BIB007 aimed more specifically toward maintaining tension arcs in interactive narratives, as well as preventing the potential deviation of the interactor from the plot. To prevent deviation, the planner is able to modify the plot in such a way as to deter or warn the interactor if they appeared to be deviating too much in action from the plot, or even risking creating a deadend, a point from which it is impossible for the interactor to reach the end of the story. Such issues highlight the challenges associated with generating interactive narratives compared to noninteractive or highly restricted hypertext narratives. In an interactive narrative, the interactor also has the ability to modify the space or even plot, and in this sense they may, intentionally or not, modify the space or plot in a way unintended by either the author or the computer. This is one of the advantages of automatic generation, since fail-safes, such as the constraints or warning techniques of the previous two systems, may be used to prevent failure. Manually authored content, on the other hand, cannot repair itself, and the interactor deviation can significantly damage or even break the plot and space itself. A classic example may be found in Morrowind  , an RPG world where the interactor may kill any character in the game world. If the interactor kills a character crucial to the plot, then the game provides a message chastising the interactor for their deviation and informing them that if they do not return to an earlier game, then they can never hope to finish the story. While many of the above systems viewed planning as a way of controlling the events present in the plot, Bae and Young instead focused on using constraints to guide the planner towards creating surprise BIB016 within the structure of the plot. The planner, called PREVOYANT makes explicit use of two narrative devices, foreshadowing and flashback, to create a sequence of events where certain events will appear surprising to the reader. Thus, while the plot is largely automated, the constraints provided are more to ensure certain reactions when reading the narrative. In a similar vein, Ware et al. developed planning techniques to generate conflict in the plot BIB017 . This again involved creating a model of conflict and, then, constraining the planner to enforce the presence of conflict in the resulting stories. This is a different approach to earlier examples, like UNIVERSE, where it is the burden of the author to author events which already contain a conflict embedded within them. 3) Interactive Narratives: Façade BIB004 is widely regarded as one of the most successful attempts at an interactive story game to have come out of the research community. In Façade, one takes the role of an acquaintance of a married couple and one is able interact with both characters using natural language text input. The plot uses constraints to ensure that certain dramatic situations occur and uses a detailed authored space to provide depth and personality to the main characters. The constraint is in the form of a dramatic arc that each story is expected to adhere to, and dramatic situations are defined as events that change certain values assigned to each of the characters (such as love or anger). Each change to a specific value is called a beat, and the game selectively picks beats one after the other such that the resulting story obeys the dramatic arc provided. IDTENSION is an interactive drama that aimed to create conflict for the interactor, as well as characters within the narrative  . As in Façade, events in the story are picked one after the other, and the system attempts to enforce a plot that creates conflict between characters. IDTENSION uses a set of moral values, toward which each character has a certain adherence. Characters with a lower adherence toward a certain moral value will be more likely to take actions which are defined as immoral with respect to that value. This results in a set of conflicting values that form the conflict in the instantiated narrative. MARLINSPIKE takes yet another unique approach to constraints BIB011 in that it attempts to create the narrative in such a way that the actions taken by the interactor become necessary to reach the stories conclusion. As with the above systems, the narrative is built incrementally with events, allowing the interactor to take an action each time. After each action, the system views a history of the interactor's actions and, then, attempts to pick an event that occurs as the result of one or more of these actions. The technique, dubbed reincorporation, aims to make the interactor feel directly involved in shaping the narrative dramatically with each action. Prom Week  utilizes a detailed social engine to model the various social interactions of high school, including gossiping, flirting, bullying, etc. An interactor can play any of the many characters within the game world and is given social goals to achieve, creating much of the emergence from the interactor's interaction between different characters. Plot in this instance is constrained both by the author, who defines several key events, most noticeably the prom itself, and by the interactor, whose interactions form events in the instantiated narrative. VERSU BIB018 is an interactive story system which relies largely on the simulation of an authored world. VERSU creates hypertext stories, in which the interactor may pick one of many potential actions a character in the world may perform. These actions, and the reactions from other characters, are all chosen procedurally based upon a detailed manual description of the space and a model of each character's personality. The author may additionally propose constraints on the plot to ensure that each instantiated narrative contains certain desired events. VERSU, like Prom Week, is unique in that the interactor may play from the perspective of any character within the story, and the choices they are presented will be appropriate for the chosen characters. Baceviciute et al. BIB012 designed an interactive story system which is used during counseling sessions with deaf children. The child models their school, giving specific personalities to different students. The system then generates conflicts between the students and the child's character during game-play. The counselor then helps the child to find solutions to these in-game conflicts, which they could then use in real life when similar situations arise. While many of the above examples focus on giving the interactor the ability to interact and even modify the space and plot, certain research instead aims to support the interactor's experience of the work by generating plots adapted to their interests or skills. The PASSAGE system monitors the interactor's actions and uses them to create a computational model of that interactor BIB005 . The AI was implemented in a sample game built in the AURORA TOOLSET [66] . The game contains multiple, generally manually authored, possible quest plots, each with annotations stating which type of interactor will most appreciate that particular plot. After completing a specific quest, the next subsequent quest is chosen by comparing the similarity between its preconditions and the current interactor model. The interactor model may also be updated based upon their behavior within each quest. Zook et al.'s military scenario generation tool BIB013 is another application of an adaptive generation tool. The aim of the system is to generate particular simulated scenarios for the interactor to train with. As the intention is to learn through repetition, the system intends to keep track of the learned experience of the interactor given their performance in the scenario. Generation is used so that the interactor does not succeed solely through trial and error, but is instead forced to learn the logic behind each scenario. For a survey on how authors, characters, and interactors may influence interactive narrative, we recommend the paper by Riedl and Bulitko BIB014 .