Boolean and Free-choice Semantics of Event-driven Process

In parallel to the successful application of Event-driven Process Chains (EPCs) in commercial IT-projects there is an ongoing scientific debate about their semantics. It is even controversial, if one should provide EPCs with a local or with a non-local semantics. In this paper, we unify two local EPC semantics, which build on Petri nets. One of them is the free-choice semantics due to the translation of EPCs into free-choice systems. The other one is the Boolean semantics, which derives from translating the EPC into a certain class of high-level Petri nets. The free-choice semantics is restricted to EPCs with only AND or XOR-connectors, but allows arbitrary loops. The Boolean semantics allows connectors of arbitrary logical type. But at this stage, it covers only EPCs with well-structured loops. For EPCs, where both semantics are defined, we derive the free-choice semantics from the Boolean semantics and show as main result: The EPC is well-formed with respect to the Boolean semantics if and only if it is well-formed with respect to the free-choice semantics. After reviewing a series of examples from the literature we continue the investigation of the Boolean semantics for EPCs with circuits different from well-structured loops.