Buffered Simulation Games for Büchi Automata

Milka Hutagalung
(University of Kassel)
Martin Lange
(University of Kassel)
Etienne Lozes
(University of Kassel)

Simulation relations are an important tool in automata theory because they provide efficiently computable approximations to language inclusion. In recent years, extensions of ordinary simulations have been studied, for instance multi-pebble and multi-letter simulations which yield better approximations and are still polynomial-time computable.

In this paper we study the limitations of approximating language inclusion in this way: we introduce a natural extension of multi-letter simulations called buffered simulations. They are based on a simulation game in which the two players share a FIFO buffer of unbounded size. We consider two variants of these buffered games called continuous and look-ahead simulation which differ in how elements can be removed from the FIFO buffer. We show that look-ahead simulation, the simpler one, is already PSPACE-hard, i.e. computationally as hard as language inclusion itself. Continuous simulation is even EXPTIME-hard. We also provide matching upper bounds for solving these games with infinite state spaces.

In Zoltán Ésik and Zoltán Fülöp: Proceedings 14th International Conference on Automata and Formal Languages (AFL 2014), Szeged, Hungary, May 27-29, 2014, Electronic Proceedings in Theoretical Computer Science 151, pp. 286–300.
Published: 21st May 2014.

ArXived at: http://dx.doi.org/10.4204/EPTCS.151.20 bibtex PDF
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