An Operational Semantics of BPMN Collaboration

In the last years we are observing a growing interest in formalising the execution semantics of business process modelling languages that, despite their lack of formal characterisation, are widely adopted in industry and academia. In this paper, we focus on the OMG standard BPMN 2.0. Specifically, we provide a direct formalisation of its operational semantics in terms of Labelled Transition Systems (LTS). This approach permits both to avoid possible miss-interpretations due to the usage of the natural language in the specification of the standard, and to overcome issues due to the mapping of BPMN to other formal languages, which are equipped with their own semantics. In addition, it paves the way for the use of consolidated formal reasoning techniques based on LTS (e.g., model checking). Our operational semantics is given for a relevant subset of BPMN elements focusing on the capability to model collaborations among organisations via message exchange. Moreover, one of its distinctive aspects is the suitability to model business processes with arbitrary topology. This allows designers to freely specify their processes according to the reality without the need of defining well-structured models. We illustrate our approach through a simple, yet realistic, running example about commercial transactions.