Comp763: Modern Computer Games Using Constraint Logic Programming to Analyze the Chronology in a William Faulkner Story Jennifer BurgSheau-Dong Lang Irwin Chiu Hau Computer Science McGill University Winter 2004

Comp763: Modern Computer Games Overview  Introduction  “A Rose to Emily” by William Faulkner  Constraint Logic Programming  The Constraint Satisfaction Algorithm and Conflict Sets  Useful Extensions  Conclusion

Comp763: Modern Computer Games Introduction  Narratives In movies: »Essential component –Every movie In games: »Interesting component –Some games

Comp763: Modern Computer Games Introduction  A good story Quality »The storyline »Character Development »Plot twist »Logical

Comp763: Modern Computer Games Introduction  A good story may have Flaws Conflicts  Human beings are Sensitive to these issues Good in spotting conflicts

Comp763: Modern Computer Games Introduction  Movies / Novels Conflicts could »Lead us to confusion »Ruin the storyline  Games Conflicts could cause serious problems »Hinder game completion

Comp763: Modern Computer Games Introduction  Dealing with conflicts Detecting Removing

Comp763: Modern Computer Games Overview  Introduction  “A Rose to Emily” by William Faulkner  Constraint Logic Programming  The Constraint Satisfaction Algorithm and Conflict Sets  Useful Extensions  Conclusion

Comp763: Modern Computer Games A Rose For Emily  Novel Written by William Faulkner Originally published on April 30, 1930  The story Not told in chronological order Broken into countless pieces Very difficult to understand

Comp763: Modern Computer Games A Rose For Emily  The challenge English literature courses »Story Analysis –Developing a list of the descriptive details associated with Emily ·Her appearance ·Surroundings – Reconstructing a chronological list of events This paper »Analysis –Events sorting –Conflicts detection

Comp763: Modern Computer Games Overview  Introduction  “A Rose to Emily” by William Faulkner  Constraint Logic Programming  The Constraint Satisfaction Algorithm and Conflict Sets  Useful Extensions  Conclusion

Comp763: Modern Computer Games Constraint Logic Programming  In this paper, CLP is applied to analyze the chronology of “A Rose for Emily”  What is CLP? Family of programming languages that allow »Declarative problem statements »Expression of constraints in specialized domains

Comp763: Modern Computer Games Constraint Logic Programming  CLP language allows a programmer to Express a problem declaratively rather than procedurally »Augmented with expression of constraints –Integers, rational numbers and Boolean values –Equations and inequalities Find a solution »Solving the system of constraints –Resolution-based inference –Constraint satisfaction

Comp763: Modern Computer Games Constraint Logic Programming  CLP is used to solve problems Circuit design Resource allocation Discrete optimization applications Analyze the Chronology in a William Faulkner Story Detecting conflicts in computer games

Comp763: Modern Computer Games CLP(R) Applied to Time Elements  Analyze the Chronology in a William Faulkner Story ··· Table 1 Variables and Their Meaning

Comp763: Modern Computer Games CLP(R) Applied to Time Elements Table 2 Constraints and Their Meaning ···

Comp763: Modern Computer Games Overview  Introduction  “A Rose to Emily” by William Faulkner  Constraint Logic Programming  The Constraint Satisfaction Algorithm and Conflict Sets  Useful Extensions  Conclusion

Comp763: Modern Computer Games The Constraint Satisfaction Algorithm  CLP program can be divided into two components An inference engine »Binding of variables A constraint solver »Each inequality constraint: a 1 x 1 + … + a n x n ≤ b »System of constraints

Comp763: Modern Computer Games Prolog  PROgramming in LOGic  A declarative language Knowledge Base »Facts Inference »Rules Query  In this paper, CLP(R) is implemented in Prolog

Comp763: Modern Computer Games Conflict Sets  The system Satisfiable Not satisfiable  Not satisfiable => There are conflicts Conflict sets

Comp763: Modern Computer Games The Conflict in "A Rose for Emily"  B ≥ E  D – E ≥ 8  E = B

Comp763: Modern Computer Games Removing the Conflict  The conflict uncovered by the CLP(R) Minimal conflict  To resolve the conflict Removing any conflicting constraint  In this example (A Rose For Emily) We choose to remove E = B And the solver finds 5 solutions

Comp763: Modern Computer Games A solution for “A Rose for Emily”

Comp763: Modern Computer Games Overview  Introduction  “A Rose to Emily” by William Faulkner  Constraint Logic Programming  The Constraint Satisfaction Algorithm and Conflict Sets  Useful Extensions  Conclusion

Comp763: Modern Computer Games Useful Extensions  CLP(R) Useful for chronological sorting of events »In stories where events are related out-of-order.  How is it related to games? Adventure games have »Events »Puzzles CLP(R) can be applied to games

Comp763: Modern Computer Games Useful Extensions  Providing an graphical interface define points in time, indicate which points are before which others give dates where dates are known ask for a sort receive a list of conflicting constraints

Comp763: Modern Computer Games Overview  Introduction  “A Rose to Emily” by William Faulkner  Constraint Logic Programming  The Constraint Satisfaction Algorithm and Conflict Sets  Useful Extensions  Conclusion

Comp763: Modern Computer Games Conclusion  Novels / Movies A story should not have any conflicts  Games Puzzles and story should not have any conflicts  CLP(R) is a powerful tool Can be used to analyze a story »Sort events »Detect conflicts

Comp763: Modern Computer Games Questions?

Comp763: Modern Computer Games