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nodes and the configurations tools of users. Ini-
tially, the configuration tools require knowledge
about the features and properties of the WSN to
be configured. Therefore, the WSN should be
enabled to describe the features it provides. Based
on these feature descriptions, the configuration
tools can even determine which kind of applica-
tion or phenomenon could be executable at all.
After specifying the application according to
the features provided, the adapted application is
submitted to the WSN. Finally, the most critical
question is: “Is the submitted application working
properly?” Means that can give a feedback about
the reliability of configured applications could
become one of the most significant advances in
convenient sensor network design.
In view of automatic WSN configuration using
the ESL and respective EDTs, those should be ap-
plied in real world scenarios like Ambient Assisted
Living (AAL) or patient monitoring systems. This
also stresses the designed support for mobility in
this approach. The ESL allows to easily customize
and configure a Body Area Network (BAN) to the
needs of a patient, e.g., by configuring thresholds
for blood pressure or body temperature. Enabling
nurses or medical employees to easily configure
a BAN for patient monitoring will be a big step
towards an ease of use for WSN configuration. In
AAL applications, like smart homes, the user may
define personal interests as an event specification,
which can be used to configure the local ambient
sensor network around the user.
Some extensions of the ESL are possible and of
interest for further research. The ESL may support
other execution constraints to allow configura-
tion of resource-oriented execution intervals, for
example. This could be scaling of the EDT evalu-
ation interval due to drained energy resources. In
addition, the XML style of the ESL should allow
to provide configuration means for WSNs by the
use of web technologies and web services. This
may further automate the configuration process
and enable remote configuration via the Internet.
The concept of EDT has to be enhanced to en-
able self-configuration of new nodes by sharing
of EDTs during runtime. This may significantly
improve the maintenance of a sensor network by
allowing newly deployed nodes to populate with
the EDTs from their neighboring nodes without
having the binary event specification available.
This allows to easily rebuilding the sensor network
in areas where nodes have crashed or the node
density has to be increased.
Furthermore, the robustness and performance
of collaboration could also be extended. Sensor
nodes could dynamically resize the applied col-
laboration region with respect to the local node
density, the specified collaboration region and a
determined preferred number of available publish-
ers. For random distributions, the nodes in areas
with low density may use the maximum configured
collaboration region. In contrast to that, the nodes
in areas with a high density may apply smaller col-
laboration regions, which still provide a sufficient
number of potential publishers. The simulations
indicated that the lease-based publish/subscribe
approach may possibly hold EDT node values
even if the respective publisher has failed during
the leasing time. In the simulation scenarios, this
caused false positive notification of events. En-
abling neighboring nodes to recognize and signal
failed devices to subscribing sensor nodes may
possibly enhance the detection accuracy further.
CONCLUSION
The envisioned pervasiveness of WSNs faces two
major problems. These are high fault probability
and configuration complexity. First, an ease of
use for task definition and configuration of WSNs
is the key to make them widely accepted. Means
that provide a high abstraction of WSNs are in
demand. These must enable also non-professional
users, which are usually short on experience of
programming languages and sensor networks, to
make use of WSNs. Second, pervasive WSNs
consisting of large numbers of devices demand to
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