Efficient processing of unlimited and continuously expanding sequences of data items is one of the key factors in the implementations of Data Stream Management Systems (DSMS). Analysis of stream processing at the dataflow level reveals execution plans which are not visible at a logical level. This work introduces a new model of data stream processing and discusses a number of optimization techniques applicable to this model and its implementation. The optimization techniques include applications of containers with intermediate results, analysis of data processing rates, and efficient synchronization of elementary operations on data streams. The paper also describes the translation of logical level expressions on data streams into the sets of dataflow level expressions, syntax based optimization of dataflow expression, and scheduling of concurrent computations of the dataflow expressions.

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Malicious attacks on Web servers by intruders and hackers are prime concerns of organizations, administrators of Web sites, as well as users who access them.

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