Technology

How Michael Mateas and Andrew Stern developed Facade to enable generative storytelling.
The most significant aspect of a computer game is the ability to engage in logical mechanical processes to which end users can assign meaning (Mateas  Stern, 2007, p.1). There are numerous tools that can enable end users manage various capacities of a computer such as manipulation of images with no need for the users to think systematically. Humans look at these computer games as a novel expressive kind similar to opera, drama and movies (Murray et al, 2006, p.43).The aim of this paper is to illustrate this assertion by describing how Michael Mateas and Andrew Stern developed Facade to enable generative storytelling.

Faade is a simulated intelligence-based research test in electronic narrative that attempt to progress beyond traditional branching narrative to develop a wholly-realized, one-act interactive drama. The process of building Faade entails three major research efforts devising ways to deconstruct a spectacular narrative into a ladder of story and behavior pieces, engineering an artificial intelligence system to reconstruct a real time impressive performance from those pieces that amalgamates the end-users moment-by-moment interfaces, and understanding how to write a compelling storyline within this novel organizational structure (Mateas  Stern, 2002a).

Similar to contemporary games, Faade is developed in a simulated world with a 3D real-time animation and sound that provides the end-user a first- person, uninterrupted, direct interface with unlimited navigation and the capability of selecting and using objects. Faade employs unconstrained natural language and emotional signal as the principal mode of expression for all characters, including the end-user (Mateas  Stern, 2007, p.5). The storyline is about the emotional situations of human relationships, such as the termination of marriage (Louchart et al, 2004, p.7). There is unity of time and space and the drama occurs in an apartment. Many authors have encountered significant challenges while developing interactive stories such as how to structure a story to include interface and retain an enjoyable and well developed plot that can be experienced by the player. The following section looks at how Mateas and Stern developed Faade to address this challenge.

Story Design
Mateas and Stern have organized Faades content pieces into compound, mixable hierarchical ranks, serialized by procedures written in several mixable authoring languages. Faades social games are structured around a numeric score, (the interface between the player and character). They have numerous levels of abstraction distinguishing atomic player connections from alterations in social score. Rather than firing a gun or jumping over barriers, Faade players fire off an array of discourse actions in natural language, such as criticism, praise, provocation and flirtation (Mateas  Stern, 2007, p.6). Although these discourse acts produce swift reactions from the characters, it may require story-context precise patterns of discourse acts to influence the social game score.

Moreover, the score is directly communicated to the player through enriched theatrical dramatic performance rather than via sliders or numbers. For instance, as a friend is invited for drinks at a make or break moment in the failing marriage of the central character Grace and Trip, the player unintentionally becomes an adversary of sort, forced by Grace and Trip into playing emotional head games with them. In the first part of the game, Grace and trip construe all of the players conversation acts in terms of a zero-sum affinity game that decides whose side Grace and Trip presently believe the player take. Concurrently, the hot-button game is taking place in which the player can prompt provocative topics such as divorce or sex, progressing through levels to gain more back story and characters information (Mateas  Stern, 2007, p.6). The second part of the story is systematized around the therapy game where the player increases each characters level of self realization about their own problem, symbolized internally as a series of counters. The system monitors the overall story tension level, which is affected by the moves the player makes in the various social games (Mateas  Stern, 2007, p.7).

Coherent Intermixing
In order to execute Faades social games as focused, logical and well placed narratives, Mateas and Stern separated the narrative into multiple fronts of progression. Secondly, they developed a variety of narrative sequencers to serialize these multiple narrative progressions. The procedural sequencers function in parallel and can logically inter mix their performances with one another (Mateas  Stern, 2007, p.7).The following section describes the faades architecture and content structure in detail.

Architecture and content Framework
The Faade system is made up of numerous procedural subsystems that function concurrently and communicate with each other 11, 12, 13, 14 15. The dynamic and systematic performance of characters Grace and Trip (how they carry out dialogue, express emotions, how they pursue players around and utilize objects) are coded as a vast compilation of behaviors. These are short reactive actions symbolizing numerous goals and sub goals for the characters, organized in an infinite, hierarchical, vigorously-changing tree structure. These behaviors are coded in a reactive planning language known as A Behavior Language (ABL) that controls both parallel and sequential behavior interfaces such as conflict, sub-goal success and failure and context conditions (Mateas  Stern, 2007, p.7).

The narrative sequencer (drama manager) for the Faade social games serialize dramatic beats (large groups of behaviors structured around a specific topic) according to specifications coded in a custom drama management language. Another subsystem is made up of a set of instructions that understand and interpret natural language (NL) and gestural input of the player. When a player enters discourse, the NL deduces one or more meanings. The second set of rules (reaction proposers) then interpret these dialogue acts in context specific ways such as provocation, agreement or alliance and remit this interpretation to the behaviors and drama manager to respond to (Mateas  Stern, 2007, p.8).

Beats, Beat Mix-in and Beats Goals
A Faade beat is made up of about 9 to 98 joint dialogue behaviors (JDB), coded in ABL. Each beat is a narrative sequencer that serializes a subset of its JBDs in reaction to player interface. JDBs are made up of a maximum of 200 lines of ABL code. A beats JDB are structured around a common narrative goal such as a short conflict about a topic, like Graces fascination with redecorating or Trips effort to compel Grace to enjoy their honeymoon in Italy (Mateas  Stern, 2007, p.8). There are uses of JDB within beat mix-ins and beat goals.

A beat is made up of a canonical sequence of narrative goals known as beat goals. The canonical sequence comprises a transition-in goal that offers a narrative transition into the beat (such as bringing up a new topic and linking it to the previous one). In addition, there is a set of Meta behaviors, known as handlers which wait for precise interpretations of player discourse acts and transform the canonical sequence using beat mix-ins.

Global Mix-in Progressions
Global mix-in is another type of narrative sequencer that functions in parallel to beat mix-in and beat goals. Each category of global mix-in has three levels that gradually dig deeper into a topic. Advancement of levels is effected by player interface such as referring to the topic. Each level in the progression is developed from one or several JDBs. They focus on topics such as sex, marriage, divorce or about objects like furniture, wedding photo, and drinks or as generic reaction to criticism, praise, opposition and flirtation (Mateas  Stern, 2007, p.10).

Conclusion
Mateas and Stern have also employed several strategies to achieve coherency in terms of dialogue management and narrative flow.  Global mix-in progression are coded to be independent of any beats narrative flow. For instance, while arguing about their second honeymoon in Italy or quibbling about the type of drinks Trip should serve, the discourse is augmented with issues such as wedding photo or sex (triggered by a players reference to their topics). Each mix-in discourse is coded and voice-acted as if they are somewhat tangential topics that are being introduced into the flow of the dialogue- oh, that photo, yeah, its really (Mateas  Stern, 2007, p.11). Therefore, mechanisms exist for managing interruptions.

Current games are designed almost exclusively around physical action. Players are restricted to operating weapons, jumping, fighting and controlling vehicles. Mateas and Stern (2002b, p.2) have revolutionized computer game industry by developing architecture and a story design that fully integrates natural language processing, a new character authoring language and a novel drama manager to create an emotional and interactive drama about human relationships (Sullivan, 2007).