Active Web Alert Service for Rule Based Alerting in Sensor Web An Event Based Approach

The recent developments in sensor, computing, communication and software technologies have brought about a new concept: the Sensor Web. A Sensor Web is a macro-instrument consisting of a heterogeneous, intelligent, spatially distributed sensors deployed to monitor and explore the environment. Open Geospatial Consortium’s (OGC) Sensor Web Enablement (SWE) initiative provides an infrastructural framework to integrate autonomous sensor webs into Spatial Data Infrastructure (SDI). The integration of sensor web-based real/near real time information into SDI would culminate in a new level of spatio-temporal decision support for critical application scenarios for climate, natural resources, environment, disaster management, critical infrastructure protection, homeland security and emergency response issues. This new level of decision support is achieved by the formalized knowledge of the facts and circumstances of the environment. However, there lacks a system in current SWE architecture that incorporates the rule based facts of the real world scenarios. This research work is an effort to conceptualize and develop an alerting geo-service that is capable of incorporating real world environmental, spatial and temporal rules that will help to get an in-depth insight of the real world phenomena for better decision making. Based on the use case scenario of flood early warning, a service is envisioned and designed that allows definition of spatio-temporal and observational rules pertaining to a flood event. The service communicates with underlying Sensor Collection Services (SCS) for sensor observation data and validates the data against predefined threshold rules. The service dispatches alert notifications to the subscribers based on the fulfillment of these threshold rules. Such an alerting service is realized through an Active Web Alert Service (AWAS). The AWAS extends current SWE components by incorporating a new service for alert notification as envisioned by Open Web Service 2 (OWS 2). The AWAS is built on top of event based communication model, a new communication paradigm for distributed GI-Services. The event based communication model enables proactive communication pattern between the AWAS and SCS(s), enabling active dispatch of sensor observation data when the rules are satisfied. The event based model enables anonymous and asynchronous communication between SCS(s) and the AWAS. SCS(s) publishes its observations as events to the event service and the AWAS subscribes to the events defined by rules with the event service. A notification is sent to the subscriber AWAS when the published and subscribed events are matched.