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A sensor network is looked at as a large distributed database system in the
Cougar system developed by Cornell University. Each sensor corresponds to
a node in a distributed database system and stores part of the data. Cougar
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Jinbao Li, Zhipeng Cai, and Jianzhong Li
does not send data at each sensor to a central node for storage and processing.
It tries to process data separately within the sensor network. Resources are
saved e?±ciently and the lifetime of the sensor network is extended.
The data model in the Cougar system supports two kinds of data types:
stored data and real-time sensor data produced by sensors [2, 7, 22]. Stored
data are presented through a traditional relational model, while sensor data
are described through a time serial. The operation set in Cougar includes
relational algebraic operations and time serial operations. The inputs of relational
algebraic operations are base relations or outputs of other relational
algebraic operations. The inputs of time serial operations are base serial or
outputs of other time serial operations. Based on relational data and the time
serial data, the data model supports three operations: (1) Relational projection,
which translates a time serial to a relation. (2) Product, which takes a
relation and a time serial as input, and a new time serial is the output. (3)
Aggregation, which takes a time serial as the input and produces a relation
as the output.
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