Scalable Continuous Query System for Web Databases

Continuous Queries (CQ) help users to retrieve results as soon as they become available. The CQ keeps track of two important events. If there is any change in the source information, it immediately notifies the user about that particular change. Secondly, it also keeps track of the timer-based events, in case information is required after a fixed period of time. Existing techniques such as OpenCQ[1] and NiagaraCQ[2] are inadequate to optimise Continuous Queries. These techniques focus on defining the semantics for execution of CQ and much less effort was spent to define the tradeoffs required for evaluating the specific condition and generating a cost-effective query evaluation plan (QEP). The optimising scheme used in [1],[2] for information retrieval is not appropriate for an environment like the Internet. This paper also provides a new architecture and group optimisation strategy for the efficient retrieval of CQ on the web.