Engineering Event-Based Systems with Scopes

Event notification services enable loose coupling and they are therefore becoming an essential part of distributed systems’ design. However, the development of event services follows the early stages of programming language evolution, disregarding the need for efficient mechanisms to structure event-based applications. In this paper, the wellknown notion of scopes is introduced to event-based systems. We show that limiting the visibility of events is a simple yet powerful mechanism that allows to identify application structure and offers a module construct for the loosely coupled components in event-based systems. We are able to customize the semantics of scoped event notification services by binding meta-objects to the application structure that reify important aspects of notification delivery, like interface mappings and transmission policies. The scoping concept facilitates design and implementation by offering encapsulation and adaption of syntax and semantics of eventbased systems.