The sink sends queries to certain WSN
regions and waits for data from WNs
located in the regions selected. Because
data are being requested through
queries, attribute-based naming is
necessary to specify the properties of
data. Due to the large number of nodes
deployed, in many WSNs it is not
practical to assign global identifiers to
each node. This, along with potential
random deployment of WNs, makes it
challenging to select a specific (or a
specific set of) WNs to be queried.
Hence, data are typically transmitted
from every WN with in the deployment
region; this gives rise, however, to
significant redundancy along with
inefficiencies in terms of energy
consumption. It follows that it is
desirable to have routing protocols
that will be able to select a set of sensor
nodes and utilize data aggregation during
the relaying of data. This has led to the
development of data-centric routing
(in traditional address-based routing, routes
are created between addressable nodes
managed in the network layer mechanism).