Abstract
We present an extension of the actor model with real-time, including deadlines associated with messages, and explicit application-level scheduling policies, e.g.,“earliest deadline first” which can be associated with individual actors. Schedulability analysis in this setting amounts to checking whether, given a scheduling policy for each actor, every task is processed within its designated deadline. To check schedulability, we introduce a compositional automata-theoretic approach, based on maximal use of model checking combined with testing. Behavioral interfaces define what an actor expects from the environment, and the deadlines for messages given these assumptions. We use model checking to verify that actors match their behavioral interfaces. We extend timed automata refinement with the notion of deadlines and use it to define compatibility of actor environments with the behavioral interfaces. Model checking of compatibility is computationally hard, so we propose a special testing process. We show that the analyses are decidable and automate the process using the Uppaal model checker.
Highlights
Actors were originally introduced by Hewitt as autonomous reasoning objects [33]
In the rest of this section, we present an intuitive introduction to our methodology for modeling and the schedulability analysis framework and at the end of this section, the extension points with respect to our initial report in [40] are identified
Actors have infinite queues, but we have shown in [38] that in a schedulable system they do not put more than dmax /bmin messages in their queues, where dmax is the longest deadline for the messages and bmin is the shortest termination time of its method automata
Summary
Actors were originally introduced by Hewitt as autonomous reasoning objects [33]. Actor languages have since evolved as a powerful tool for modeling distributed and concurrent systems [3,4]. An actor consists of its methods, scheduler and queue This specification is given in timed automata [7] in order to support automated analysis techniques. In this model, deadlines are assigned to messages and explicit application-level scheduling policies are associated to the individual actors – Behavioral interface as a contract between actor and its environment [38,40] – Decidability because of queue size limit [38] – Modeling and analysis in Uppaal (introduced in [40], a complete presentation in this paper).
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