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
Decidability and Complexity Results for Timed Automata and Semi-linear Hybrid Automata
HSCC '00 Proceedings of the Third International Workshop on Hybrid Systems: Computation and Control
On the complexity of omega -automata
SFCS '88 Proceedings of the 29th Annual Symposium on Foundations of Computer Science
Theories of automata on ω-tapes: A simplified approach
Journal of Computer and System Sciences
Classes of Timed Automata and the Undecidability of Universality
Fundamenta Informaticae
Classes of Timed Automata and the Undecidability of Universality
Fundamenta Informaticae
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Universality for deterministic Timed Büchi Automata (TBA) is PSPACE-complete but becomes highly undecidable when unrestricted nondeterminism is allowed. More precisely, universality for nondeterministic TBA is Π$^1_1$-hard and its precise position in the analytical hierarchy is still an open question. In this paper we introduce two types of syntactical restrictions to nondeterministic TBA, which are of independent interest, and show that their universality problem is Π$^1_1$-complete. These restrictions define, as we prove, proper subclasses of the class of timed languages defined by nondeterministic TBA. This suggests, as we argue, that no solution to that open question will come without surprise. We also establish closure properties and the relationships between the classes of languages we describe.