Concept and Prototype for a Real-Time Enabled Publish/Subscribe System

Distributed computing systems often strive to decouple their communicating components (threads on a single node, or nodes in a network) from each other with respect to time, space/location, or flow/synchronization, so that they can operate as independently of each other as possible. One approach to let components in a distributed system communicate in such an independent, decoupled fashion is to follow a Publish/Subscribe paradigm. It is, however, not at all obvious that such distributed systems then remain capable of real-time operation. We are particularly interested in applying such features to Wireless Sensor Networks (WSNs), where a small footprint is required and traditional middleware approaches are far too heavyweight. We show that it is possible to combine the Publish/Subscribe paradigm with real-time features. We demonstrate this by a blackboard-based Publish/Subscribe system with real-time extensions that we have implemented on MANTIS OS. We show that timeliness of the system´s actions can be achieved without re-introducing tight couplings.