In this paper we propose an extension of the Rebeca language that can be used to model distributed and asynchronous systems with timing constraints. We provide the formal semantics of the language using Structural Operational Semantics, and show its expressiveness by means of examples. We developed a tool for automated translation from timed Rebeca to the Erlang language, which provides a first implementation of timed Rebeca. We can use the tool to set the parameters of timed Rebeca models, which represent the environment and component variables, and use McErlang to run multiple simulations for different settings. Timed Rebeca restricts the modeller to a pure asynchronous actor-based paradigm, where the structure of the model represents the service oriented architecture, while the computational model matches the network infrastructure. Simulation is shown to be an effective analysis support, specially where model checking faces almost immediate state explosion in an asynchronous setting.

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The success of model checking is based on its ability to uncover errors in designs of software and protocols. Even a small reactive concurrent system can exhibit complex behavior. Such systems may have state-spaces larger than explicit state model checkers can verify. In practice, finding an error with a model checker is more useful than proving a property. Informed search algorithms use heuristic strategies with problem-specific knowledge to find solutions more efficiently than uninformed algorithms. Generally, such heuristics estimate the distance from a given state to a goal state. We present seven heuristics for guiding search algorithms through the state-space of actor-based models to a deadlock. Our methods can find a deadlock more efficiently than uninformed searches for some actor-based models. The A* search algorithm guarantees an optimal solution and returns the shortest counterexample. These methods are supported by a tool that performs directed model checking of the deadlock property. The objective is to detect difficult errors that might not be found by simulation or by conventional model checkers before reaching an upper bound or state-space explosion.