How do we remember the past in randomised strategies?

Julien Cristau
(LIAFA, CNRS & Université Paris 7)
Claire David
(LFCS, University of Edinburgh)
Florian Horn
(LIAFA, CNRS & Université Paris 7)

Graph games of infinite length are a natural model for open reactive processes: one player represents the controller, trying to ensure a given specification, and the other represents a hostile environment. The evolution of the system depends on the decisions of both players, supplemented by chance.

In this work, we focus on the notion of randomised strategy. More specifically, we show that three natural definitions may lead to very different results: in the most general cases, an almost-surely winning situation may become almost-surely losing if the player is only allowed to use a weaker notion of strategy. In more reasonable settings, translations exist, but they require infinite memory, even in simple cases. Finally, some traditional problems becomes undecidable for the strongest type of strategies.

In Angelo Montanari, Margherita Napoli and Mimmo Parente: Proceedings First Symposium on Games, Automata, Logic, and Formal Verification (GANDALF 2010), Minori (Amalfi Coast), Italy, 17-18th June 2010, Electronic Proceedings in Theoretical Computer Science 25, pp. 30–39.
Published: 9th June 2010.

ArXived at: http://dx.doi.org/10.4204/EPTCS.25.7 bibtex PDF

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