Stephan Schiffel

AIJ Journal 2012 Journal Article

Automated verification of state sequence invariants in general game playing

• Sebastian Haufe
• Stephan Schiffel
• Michael Thielscher

A general game player is a system that can play previously unknown games given nothing but their rules. Many of the existing successful approaches to general game playing require to generate some form of game-specific knowledge, but when current systems establish knowledge they rely on the approximate method of playing random sample matches rather than formally proving knowledge. In this paper, we present a theoretically founded and practically viable method for automatically verifying properties of games whose rules are given in the general Game Description Language (GDL). We introduce a simple formal language to describe game-specific knowledge as state sequence invariants, and we provide a proof theory for verifying these invariants with the help of Answer Set Programming. We prove the correctness of this method against the formal semantics for GDL, and we report on extensive experiments with a practical implementation of this proof system, which show that our method of formally proving knowledge is viable for the practice of general game playing.

AAAI Conference 2011 Conference Paper

Reasoning About General Games Described in GDL-II

• Stephan Schiffel
• Michael Thielscher

Recently the general Game Description Language (GDL) has been extended so as to cover arbitrary games with incomplete/imperfect information. Learning—without human intervention—to play such games poses a reasoning challenge for general game-playing systems that is much more intricate than in case of complete information games. Action formalisms like the Situation Calculus have been developed for precisely this purpose. In this paper we present a full embedding of the Game Description Language into the Situation Calculus (with Scherl and Levesque’s knowledge fluent). We formally prove that this provides a sound and complete reasoning method for players’ knowledge about game states as well as about the knowledge of the other players.

AAAI Conference 2010 Conference Paper

Symmetry Detection in General Game Playing

• Stephan Schiffel

We develop a method for detecting symmetries in arbitrary games and exploiting these symmetries when using tree search to play the game. Games in the General Game Playing domain are given as a set of logic based rules defining legal moves, their effects and goals of the players. The presented method transforms the rules of a game into a vertex-labeled graph such that automorphisms of the graph correspond with symmetries of the game. The algorithm detects many kinds of symmetries that often occur in games, e. g. , rotation and reflection symmetries of boards, interchangeable objects, and symmetric roles. A transposition table is used to efficiently exploit the symmetries in many games.

IJCAI Conference 2009 Conference Paper

• Stephan Schiffel
• Michael Thielscher

A general game player is a system that understands the rules of an unknown game and learns to play this game well without human intervention. To succeed in this endeavor, systems need to be able to extract and prove game-specific knowledge from the mere game rules. We present a practical approach to this challenge with the help of Answer Set Programming. The key idea is to reduce the automated theorem proving task to a simple proof of an induction step and its base case. We prove correctness of this method and report on experiments with an offthe-shelf Answer Set Programming system in combination with a successful general game player.

ICAART Conference 2009 Conference Paper

Specifying Multiagent Environments Systems in the Game Description Language

• Stephan Schiffel
• Michael Thielscher

The Game Description Language (GDL) has been developed for the purpose of formalizing game rules. It serves as the input language for general game players, which are systems that learn to play previously unknown games without human intervention. In this paper, we show that GDL can be readily used as a specification language for a large class of multiagent environments. The resulting specifications are declarative, compact, and easy to understand and maintain. At the same time they can be fully automatically understood and used by autonomous agents who intend to participate in these environments. Our main result is a formal characterization of the class of multiagent environments that can be described in GDL.

AAAI Conference 2007 Conference Paper

Fluxplayer: A Successful General Game Player

• Stephan Schiffel

General Game Playing (GGP) is the art of designing programs that are capable of playing previously unknown games of a wide variety by being told nothing but the rules of the game. This is in contrast to traditional computer game players like Deep Blue, which are designed for a particular game and can’t adapt automatically to modifications of the rules, let alone play completely different games. General Game Playing is intended to foster the development of integrated cognitive information processing technology. In this article we present an approach to General Game Playing using a novel way of automatically constructing a position evaluation function from a formal game description. Our system is being tested with a wide range of different games. Most notably, it is the winner of the AAAI GGP Competition 2006.

AAAI Conference 2006 Conference Paper

Reconciling Situation Calculus and Fluent Calculus

• Stephan Schiffel
• Michael Thielscher

The Situation Calculus and the Fluent Calculus are successful action formalisms that share many concepts. But until now there is no formal relation between the two calculi that would allow to formally analyze the relationship between the two approaches as well as between the programming languages based on them, Golog and FLUX. Furthermore, such a formal relation would allow to combine Golog and FLUX and to analyze which of the underlying computation principles is better suited for different classes of programs. We develop a formal translation between domain axiomatizations of the Situation Calculus and the Fluent Calculus and present a Fluent Calculus semantics for Golog programs. For domains with deterministic actions our approach allows an automatic translation of Golog domain descriptions and execution of Golog programs with FLUX.