Microservices-Aware Business Process Modelling

Microservices Architecture (MSA) is the de facto software architecture approach for highly scalable software systems. Organisations must design their structure and processes around business outcomes to reap MSA's benefits. Also, MSA requires the domain model for each microservice to be minimal and avoid coupling with other microservices' domain entities. However, such coupling might already occur during the design of the business process and then propagate along the development life cycle. The first opportunity to prevent coupling occurs while designing collaborations between different participants (organisational units, such as development teams) since assigning business responsibilities defines how much domain knowledge each participant must handle. This paper proposes a method to design business process models so the domain managed by each process participant matches the size and complexity required for MSA domain design, enabling the seamless use of MSA. We reviewed nine code repositories to characterise the size and complexity of MSA domain models and proposed a metamodel conceptualising the optimal microservice domain model. Then, taking as input BPMN's Choreography diagrams describing interactions among participants, we propose (i) to specify the structure of the messages interchanged by the choreography participants, (ii) a set of process modelling guidelines to avoid domain coupling by preventing coarse interactions and heavy domain-savvy process participants, and (iii) a set of transformation guidelines to systematically derive the MSA domain model from the message structures. This contribution aims to help business process designers envision the domain complexity each process participant handles and prevent coupling business domains during process design. We provide a detailed example showing the approach's feasibility and discuss the proposal's implications, benefits and limitations.