Query Plan Execution in a Heterogeneous Stream Management System for Situational Awareness

Battlefield monitoring involves collecting streaming data from different sources, transmitting the data over a heterogeneous network, and processing queries in real-time in order to respond to events in a timely manner. Nodes in these networks differ with respect to their processing, storage and communication capabilities. Links in the network differ with respect to their communication bandwidth. The topology of the network itself is subject to change, as the nodes and links may become unavailable. Continuous queries executed in such environments must also meet some quality of service (QoS) requirements, such as, response time, throughput, and memory usage. We propose that the processing of the queries be shared to improve resource utilization, such as storage and bandwidth, which, in turn, will impact the QoS. We show how multiple queries can be represented in the form of an operator tree, such that their commonalities can be easily exploited for multi query plan generation. Query plans may have to be updated in this dynamic environment (network topology changes, arrival of new queries, arrival pattern of streams altered), this, in turn, necessitates migrating operators from one set of nodes to another. We sketch some ideas about how operator migration can be done efficiently in such environments.