Event-Driven Mashup Orchestration with Scala

We describe the organization of a Server-side platform supporting the execution of Event-Driven Mashups (i.e., composite applications combining services and smart objects through events). To support a large number of concurrent Mashup executions, Mashup Execution Platforms (MEPs) must exploit the processing power of multi-processor computer architectures as well as appropriate concurrency models and programming languages. In order to do so, we describe a MEP based on the emerging Scala programming language which provides an efficient concurrency model -- based on the actor model -- that is suitable for the execution on multi-processor systems. Since the MEP architecture considered in this paper has been previously implemented in Java we also describe its porting from Java to Scala taking advantage of the compatibility between the two programming languages. Finally, the Java-based and the Scala-based implementations are compared from a performance point of view.