Theoretical Computer Science
Real-time system = discrete system + clock variables
Theories and experiences for real-time system development
Theories of programming languages
Theories of programming languages
An algebraic framework for urgency
Information and Computation
Modeling Urgency in Timed Systems
COMPOS'97 Revised Lectures from the International Symposium on Compositionality: The Significant Difference
On the Composition of Hybrid Systems
HSCC '98 Proceedings of the First International Workshop on Hybrid Systems: Computation and Control
HSCC '01 Proceedings of the 4th International Workshop on Hybrid Systems: Computation and Control
Kronos: A Model-Checking Tool for Real-Time Systems
CAV '98 Proceedings of the 10th International Conference on Computer Aided Verification
IF-2.0: A Validation Environment for Component-Based Real-Time Systems
CAV '02 Proceedings of the 14th International Conference on Computer Aided Verification
Modelling Timeouts without Timelocks
ARTS '99 Proceedings of the 5th International AMAST Workshop on Formal Methods for Real-Time and Probabilistic Systems
The Compositional Specification of Timed Systems - A Tutorial
CAV '99 Proceedings of the 11th International Conference on Computer Aided Verification
The coarsest congruence for timed automata with deadlines contained in bisimulation
CONCUR 2005 - Concurrency Theory
Specifying Urgency in Timed I/O Automata
SEFM '05 Proceedings of the Third IEEE International Conference on Software Engineering and Formal Methods
MODEST: A Compositional Modeling Formalism for Hard and Softly Timed Systems
IEEE Transactions on Software Engineering
Lost in Translation: Hybrid-Time Flows vs. Real-Time Transitions
HSCC '08 Proceedings of the 11th international workshop on Hybrid Systems: Computation and Control
Notions of bisimulation and congruence formats for SOS with data
Information and Computation
Foundations of a compositional interchange format for hybrid systems
HSCC'07 Proceedings of the 10th international conference on Hybrid systems: computation and control
Operational semantics of hybrid systems
HSCC'05 Proceedings of the 8th international conference on Hybrid Systems: computation and control
Repairing time-determinism in the process algebra for hybrid systems ACPhssrt
Theoretical Computer Science
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The extension of timed formalisms to a hybrid setting with urgency, has been carried out in a rather straightforward manner, seemingly without difficulty. However, in this paper, we show that the combination of urgency with abstraction from continuous variables leads to undesired behavior. Abstraction from continuous variables ultimately leads to a timed system again, but with a much richer set of possible branching behaviors than a timed system that comprises only clocks. As it turns out, the formal definition of urgency, as defined for timed systems with clocks, does not fit our intuition of urgency anymore when applied to a timed system that is an abstraction of a hybrid system. Therefore, we propose to extend the formal semantics of timed and hybrid systems with guard trajectories. In this way, the continuous branching behavior introduced by hybrid systems remains visible even after abstraction from continuous variables. The practical applicability of the introduction of guard trajectories is illustrated by our revision of the structured operational semantics of the CIF language. The interplay between urgency and abstraction now adheres to our intuition, while compositionality with respect to urgency, variable abstraction, and parallel composition, is retained. In the future, symbolic elimination of urgency can be used to ensure that guard trajectories do not need to be actually calculated.