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Published in:
2008 | OriginalPaper | Chapter
Emptiness of Multi-pushdown Automata Is 2ETIME-Complete
Authors : Mohamed Faouzi Atig, Benedikt Bollig, Peter Habermehl
Published in: Developments in Language Theory
Publisher: Springer Berlin Heidelberg
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We consider
multi-pushdown automata
, a multi-stack extension of pushdown automata that comes with a constraint on stack operations: a pop can only be performed on the first non-empty stack (which implies that we assume a linear ordering on the collection of stacks). We show that the emptiness problem for multi-pushdown automata is 2ETIME-complete wrt. the number of stacks. Containment in 2ETIME is shown by translating an automaton into a grammar for which we can check if the generated language is empty. The lower bound is established by simulating the behavior of an alternating Turing machine working in exponential space. We also compare multi-pushdown automata with the model of bounded-phase multi-stack (visibly) pushdown automata.