Abstract.
We consider stochastic turn-based games where the winning
objectives are given by formulae of the branching-time logic
PCTL. These games are generally not determined and winning strategies may require memory and/or randomization.
Our main results concern history-dependent strategies. In
particular, we show that the problem whether there exists
a history-dependent winning strategy in 1 12 -player games
is highly undecidable, even for objectives formulated in the
L(F=5/8, F=1, F>0, G=1) fragment of PCTL. On the other
hand, we show that the problem becomes decidable (and in
fact EXPTIME-complete) for the L(F=1, F>0, G=1) fragment of PCTL, where winning strategies require only finite
memory. This result is tight in the sense that winning strategies for L(F=1, F>0, G=1, G>0) objectives may already require infinite memory.
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