PSWare: A publish / subscribe middleware supporting composite event in wireless sensor network

Middleware for wireless sensor network (WSN) has been proposed as an effective solution to ease the application development by providing high-level abstractions. One of the important tasks of middleware in WSN is to support event service. As an important paradigm for event service, publish / subscribe (pub/sub) can support the asynchronous data exchange for applications and has received a lot of attention in traditional distributed systems. In WSNs, however, the design of pub/sub, especially on composite events, has not been adequately addressed. In this paper, we present the design and implementation of PSWare, a pub / sub middleware for WSN which can support both primitive and composite events. Our contribution mainly includes three parts. First, we propose an event definition language (EDL), which is specifically tailored to WSNs and can achieve high expressiveness and availability in the definition of primitive and composite events. The application programmers of PSWare can use the proposed EDL to define events in a simple manner. We implemented a compiler to compile the program written in EDL into byte codes. Second, we develop a runtime environment on sensor nodes, which provide a platform to run the compiled byte codes. Finally, we propose a composite event detection protocol to detect the events in an energy-efficient fashion.