Timed Pushdown Automata Revisited

This paper contains two results on timed extensions of pushdown automata (PDA). As our first result we prove that the model of dense-timed PDA of Abdulla et al. Collapses: it is expressively equivalent to dense-timed PDA with timeless stack. Motivated by this result, we advocate the framework of fir...

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Bibliographic Details
Published in:2015 30th Annual ACM/IEEE Symposium on Logic in Computer Science pp. 738 - 749
Main Authors: Clemente, Lorenzo, Lasota, Slawomir
Format: Conference Proceeding
Language:English
Published: IEEE 01.07.2015
Subjects:
Atomic clocks
Automata
Complexity theory
Handheld computers
orbit-finite
Orbits
pushdown automata
Registers
sets with atoms
timed automata
ISSN:1043-6871
Online Access:Get full text
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Summary:This paper contains two results on timed extensions of pushdown automata (PDA). As our first result we prove that the model of dense-timed PDA of Abdulla et al. Collapses: it is expressively equivalent to dense-timed PDA with timeless stack. Motivated by this result, we advocate the framework of first-order definable PDA, a specialization of PDA in sets with atoms, as the right setting to define and investigate timed extensions of PDA. The general model obtained in this way is Turing complete. As our second result we prove NEXPTIME upper complexity bound for the non-emptiness problem for an expressive subclass. As a byproduct, we obtain a tight EXPTIME complexity bound for a more restrictive subclass of PDA with timeless stack, thus subsuming the complexity bound known for dense-timed PDA.
ISSN:1043-6871
DOI:10.1109/LICS.2015.73