Putting events in context: aspects for event-based distributed programming

Event-based programming is an appealing paradigm for developing pervasive systems since events enable the decoupling of interacting components. Unfortunately, many event-based languages and systems have hardwired notions of physical or logical time and space. This limits their adaptability and target deployment environments, as pervasive systems rely on inherent interaction and interchanging of different protocols and infrastructures. This paper introduces domain-specific aspects for capturing event context, generalizing beyond the classic time and space dimensions associated with events. Through examples, we demonstrate that our context aspects - conspects for short - modularize the design and implementation of event contexts, enabling code reuse, and making programs portable across infrastructures. We illustrate the benefits of conspects by using them to transparently switch protocols in two pervasive software suites implemented in EventJava: (1) a tornado monitoring system deployed on different architectures ranging from desktop x86 to embedded LEON3, and (2) a mobile social networking suite with protocols for different application scenarios.