Analysis of Event-Driven Service Interactions: Choreography Versus Orchestration Approach

Implementing event-driven behavior involves an approach where a preceding event occurrence triggers each action within a system. Business processes, often built using distributed, autonomous, communicating web services, frequently exhibit such behavior patterns during their execution. Two approaches emerge in integrating web services into business processes: choreography and orchestration. Choreography supports loosely coupled services that are unaware of being part of a larger scenario, and they can only be integrated through an event occurrence mechanism, i.e., by exchanging messages via a shared message container where the receipt of a message is treated as an event occurrence. Orchestration, on the other hand, implies an approach that requires the existence of a central coordinator, which usually calls services according to a predefined execution sequence. In this case, the execution does not necessarily have to be event-driven; it proceeds according to the business process definition stored on the coordinator side. This paper analyzes the possibilities for creating event-driven interactions in both approaches. It examines their complexity, advantages, and disadvantages, as well as decision-making scenarios regarding which approach would be more optimal based on the existing integration conditions.