176 research outputs found
Action Contraction
The question we consider in this paper is: āWhen can a combination of fine-grain execution steps be contracted into an atomic action executionā? Our answer is basically: āWhen no observer can see the difference.ā This is worked out in detail by defining a notion of coupled split/atomic simulation refinement between systems which differ in the atomicity of their actions, and proving that this collapses to Parrow and Sjƶdinās coupled similarity when the systems are composed with an observer
Metric Semantics and Full Abstractness for Action Refinement and Probabilistic Choice
This paper provides a case-study in the field of metric semantics for probabilistic programming. Both an operational and a denotational semantics are presented for an abstract process language L_pr, which features action refinement and probabilistic choice. The two models are constructed in the setting of complete ultrametric spaces, here based on probability measures of compact support over sequences of actions. It is shown that the standard toolkit for metric semantics works well in the probabilistic context of L_pr, e.g. in establishing the correctness of the denotational semantics with respect to the operational one. In addition, it is shown how the method of proving full abstraction --as proposed recently by the authors for a nondeterministic language with action refinement-- can be adapted to deal with the probabilistic language L_pr as well
A categorical view of action refinement in models of concurrency
We define a categorical characterization of refinement and show that refinement definitions for various models of concurrency can be captured be our view
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