Translating Orc Features into Petri Nets and the Join Calculus

Cook and Misra’s Orc is an elegant language for orchestrating distributed services, able to cover e.g. van der Aalst’s workflow patterns. We aim to understand the key novel features of Orc by comparing it with variations of Petri nets. The comparison shows that Orc hides powerful mechanisms for name handling (creation and passing) and for atomic distributed termination. Petri nets with static topology can encode Orc under severe restrictions while the full language (up to a more realistic cancellation strategy) can be encoded in Join (that can be seen as a higher-order extension of Petri nets). As an overall result, we promote Join calculus as an elegant language embedding orchestration and computation.