Global vs. local semantics of BPMN 2.0 OR-join

Nowadays, BPMN 2.0 has acquired a clear predominance for modelling business processes. However, one of its drawback is the lack of a formal semantics, that leads to different interpretations, and hence implementations, of some of its features. This, as a matter of fact, results on process implementations using such features that do not fit with designers expectations, and that are not portable from one BPMN enactment tools to another. Among the BPMN elements particular ambiguous is the semantics of the OR-Join. Several formalisations of this element have been proposed in the literature, but none of them is derived from a direct and faithful translation of the current version of BPMN standard. In this work we instead provide direct, global and local, formalisations compliant with the OR-Join semantics reported in the BPMN 2.0 standard. In particular, the local semantics is devised to more efficiently determine the OR-Join enablement. The soundness of the approach is given by demonstrating the correspondence of the local semantics with respect to the global one.