Prof. Diletta Romana Cacciagrano

(red-cong) :

α α CONG

α α

Early and late LTSs

L

L

L

Theorem:

Name instantation is moved inside the definition of bisimulation. The open bisimilarity, written, is the largest open bisimulation.

A set of processes to be test. A set of tests or observers. These are obtained by extending the syntax of processes to generate processes which can perform a particular action (omega) reporting success. A way to exercise a process on a given test: it is done by letting the process and the test to run in parallel and by looking at the computations which the embedded process can perform. These computations can be successful or failing, depending on whether or not they allow the execution of omega. A general criterion (semantics) for interpreting the results of these exercises.

Observer (Tests) Experiments

Bisimulation equivalences are usually rather strict: they depend on the whole branching structure of processes which, in some cases, are not relevant. Weak bisimulation incorporates a particular notion of fairness: it abstracts from the tau-loops (i.e infinite sequences of tau-moves): the “normal” behavior can be resumed each time after a finite sequence of tau-moves. Must testing semantics is based on the interpretation of tau-loops as divergences, making them quasi-observable as a chaotic or under- specified behavior. For this, it has been defined fair-testing semantics. The standard testing equivalences are coarser than weak bisimulation in the case of divergence-free processes, and they are incomparable in general.