Theory of recursive functions and effective computability
Theory of recursive functions and effective computability
On verifying that a concurrent program satisfies a nondeterministic specification
Information Processing Letters
Theoretical Computer Science
Symbolic model checking for real-time systems
Information and Computation
The complexity of probabilistic verification
Journal of the ACM (JACM)
Timed automata and recognizability
Information Processing Letters
Achilles and the Tortoise climbing up the hyper-arithmetical hierarchy
Theoretical Computer Science - Special issue on real numbers and computers
Achilles and the tortoise climbing up the arithmetical hierarchy
Journal of Computer and System Sciences - Fourteenth ACM SIGACT-SIGMOD-SIGART symposium on principles of database systems
The Expressive Power of Clocks
ICALP '95 Proceedings of the 22nd International Colloquium on Automata, Languages and Programming
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Universality for deterministic Timed Büchi Automata (TBA)is PSPACE-complete but becomes highly undecidable when unrestrictednondeterminism is allowed. More precisely, universality fornondeterministic TBA is Π^1_1-hard and its precise position inthe analytical hierarchy is still an open question. In this paperwe introduce two types of syntactical restrictions tonondeterministic TBA, which are of independent interest, and showthat their universality problem is Π^1_1-complete. Theserestrictions define, as we prove, proper subclasses of the class oftimed languages defined by nondeterministic TBA. This suggests, aswe argue, that no solution to that open question will come withoutsurprise. We also establish closure properties and therelationships between the classes of languages we describe.