Networking Reference
In-Depth Information
Fig. 3.5 REST service provided by PEM to discover the WSNs registered in the SmartSensor
Fig. 3.6 XML file returned
as the output of a call to
GetServices representing the
services provided by a WSN
connected to the SmartSensor
can obtain the information (sensing data) already stored in the SIMdatabase, or make
a new request for data. Figure 3.6 shows an XML file representing an example of
the outcome of a call to GetServices that presents the services (type of sensor data)
offered by a given WSN connected to the SmartSensor. In this example the nodes
(from Arduino platform) provides temperature and distance services.
To find out which sensors are available in a given WSN that provide data of a spe-
cific type, SmartSensor provides other service, accessed via URI: http://SIM_server/
gateway/rest/getdata/type_of_sensor . Then, the user can send a request to a specific
node to perform a specific service, by using the generic URI: http://SIM_server/
gateway/rest/request/id_sensor/type_of_sensor ; or he/she can request data from a
specific type (for instance, light, temperature, acceleration, etc) from a given WSN
without specifying any particular node (this is the most frequent case in WSNs).
Figure 3.7 shows anXMLfilewith historical temperature data returned froma request
for the temperature service of a specific node (in this example, node with ID
11).
Besides the types of sensing data available in the sensor nodes, other relevant
metadata are kept in the SIM database (more details on this in Chap. 4 ) , such as QoS
parameters, geographical location, among others. However, in the current implemen-
tation of SmartSensor, only searches for types of sensors or for specific nodes are
available.
The interactions within the domain of a given WSN occur basically as follows
(Fig. 3.8 ). Suppose a request from a client application is sent to the SIM Gateway,
which is continuously listening for incoming requests. This part of communication
=
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