It is a small software for query processing
in a sensor network. GUI is implemented by Java and runs on any
platform that supports Java and Swing. The QueryProxy and FrontEnd are
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Chapter 12 Data Management in Sensor Networks
Fig. 19. The Architecture of COUGAR [7, 4].
built using C++ and run under Linux on either x86 or Sensoria WINS NG
node hardware.
Communications within the sensor network are transmitted using Directed
Di?®usion and are formatted as XML. The GUI and FrontEnd communicate
over TCP/IP sockets. Let us briefly introduce QueryProxy, FrontEnd and
GUI.
QueryProxy
The QueryProxy consists of three parts: the device manager, the node
layer, and the leader layer. Cougar divides the nodes in the sensor network
into several clusters. Each cluster contains several nodes but only one leader.
The sensor nodes are capable of acting as leaders or normal query processing/
signal processing nodes. When the network is set up, clusters are formed
and leaders are elected from the nodes in the clusters. The QueryProxy system
has a hierarchical structure, with the FrontEnd communicating with nodes
that act as cluster leaders, and with cluster leaders communicating with the
FrontEnd and with the other sensor nodes in their clusters. The device manager
takes readings from the sensors. The node layer manages the execution
of queries on the sensor node and the interaction with the sensors via the
device manager.
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