The nodes at proxy network
layer have high computation, storage and communication capabilities. Proxies
have five functions: receiving queries from users, issuing control commands and
other information to sensors, receiving data from sensors, processing queries,
and delivering query results to users. After receiving data from sensors, instead
of relaying all data to a central server for processing, each proxy processes the
query in a decentralized way and delivers the results to the users. From the
above introduction, we can see that computation and communication loads
are distributed among all proxies.
3 Data Model and Query Language in Sensor Networks
3.1 Data Model
There are a lot of research works on the data model in sensor networks.
These research works mainly focus on limited extensions of the traditional
relational model, object relational model and time serial model. Some research
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Chapter 12 Data Management in Sensor Networks
Fig. 3. Hierarchical model [9].
works regard sensor data as relations in multiple nodes and regard a sensor
network as a distributed database. Some other research works regard a whole
sensor network as a distributed database system composed of some distributed
data streams. Other research works use a time serial and probability model
to represent the time features and the uncertainty of sensor data. TinyDB
developed by UC Berkely [15, 10, 21] and the COUGAR system developed by
Cornell [3, 4] are two examples to introduce the data model in sensor networks.
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