Verification of Computation Orchestration Via Timed Automata

Recently, a promising programming model called Orc has been proposed to support a structured way of orchestrating distributed web services. Orc is intuitive because it offers concise constructors to manage concurrent communication, time-outs, priorities, failure of sites or communication and so forth. The semantics of Orc is also precisely defined. However, there is no verification tool available to verify critical properties against Orc models. Instead of building one from scratch, we believe the existing mature model-checkers can be reused. In this work, we first define a Timed Automata semantics for the Orc language, which we prove is semantically equivalent to the original operational semantics of Orc. Consequently, Timed Automata models are systematically constructed from Orc models. The practical implication of the construction is that tool supports for Timed Automata, e.g., UPPAAL, can be used to model check Orc models. An experimental tool is implemented to automate our approach.