A SOA Approach to Delay and Jitter Tolerant Distributed Real-Time Complex Event Processing

The combination of Service Oriented Architectures (SOAs) and Complex Event Processing (CEP) is gaining momentum for event centric management and processing of information in complex distributed systems (e. g., business automation). Whereas systems for factory automation have traditionally been deployed using dedicated buses and proprietary (often scan based) protocols, a recent trend in process automation is towards adopting open internet based technologies and event based communication. This trend is driven by the increasing number and capabilities of devices used for monitoring and control, and the increased flexibility, maintainability and price/performance gains expected from IP (potentially SOA/CEP) enabled systems. In this paper we discuss the challenges involved to apply SOA and CEP to the field of factory automation. In particular, real-time aspects are highlighted, both w.r.t. to accurate time-stamping of physical events in a distributed system, as well as end-to-end timing including communication and CEP processing. We approach the challenges by an architecture combining state-of-the-art synchronisation mechanisms for wired and wireless networks together with real-time communication and distributed query processing based on the notion of time constrained reactions. We discuss the impact of synchronisation inaccuracies and delays introduced by processing and communication, and present a method for implementation of safe potential-and certain matches.