A query-matching mechanism over out-of-order event stream in IOT
International Journal of Ad Hoc and Ubiquitous Computing
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The increasingly wide range of RFID applications and the characteristics of RFID data, such as massive, continuous, require RFID middleware to provide efficient, real-time data processing capability, and to support to extract meaningful complex event from meaningless simple low-level events. OSGi is a kind of lightweight, loosely coupled, service-oriented application development framework. System based on OSGi can install, start, stop and uninstall certain components of the system in the run-time environment if application needs, because the system has some features like component-based, reconfigurable and dynamic management. This paper discusses the overall technology solutions of RFID middleware into which the OSGi technology is added. By adding complex event processing layer based on OSGi into RFID middleware, the middleware can detect complex event defined by the application and accept the query modification without stopping. Considering out-of-order event from event source, the paper presents the improved detection algorithm for out-of-order event which is the extension of the traditional data stream approach and causes complex event detection more practical and precise.