SANY D2.3.4 Specification of the Sensor Service Architecture V3 Doc.V3.1
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Figure 5-4: Model of a Sensor System
In contrast to a complex form of a sensor, the sensor system allows direct addressing of its individual parts as well as addressing of the sensor system as a unit. A complex form of a
sensor provides only the management of the whole entity. Individual parts are not directly addressable. The difference affects the management interface, but has no influence on
the response behaviour of both, complex form of a sensor as well as sensor system. Both might provide data that traces back to individual parts.
5.3. Enterprise Viewpoint of a Sensor
The enterprise viewpoint analyses the business context and the system and user requirements for environmental monitoring in terms of functionality, information demand and quality. It
identifies the environmental phenomena that have to be observed with their temporal and spatial resolution and reflects this need with the types of sensors and models that are
available. This activity may encompass a cost-benefit analysis if there are several options and offers of service providers. Furthermore, from the set of requirements basic patterns of sensor
topologies are abstracted see section 4.5. As listed in Table 4-1, a distinction has to be maintained between sensors and corresponding data loggers that are spatially fixed, i.e. bound
to a given location, and mobile sensors such as cameras on aircrafts or satellites.
5.4. Engineering Viewpoint of a Sensor
Roughly speaking, the engineering viewpoint links components to a communication network. The network might be the Internet or any other open communication network. The
components themselves implement purposes, functions, and content as described in the
SANY D2.3.4 Specification of the Sensor Service Architecture V3 Doc.V3.1
Copyright © 2007-2009 SANY Consortium Page 53 of 233
service and information viewpoint below. Thus, the sensor model is extended with a network node component e.g. an Internet node as illustrated in Figure 5-5.
The SensorSA defines the resulting sensor network as a collection of sensors and
optional processing nodes, in which information on properties observed by the sensors may be transferred and processed.
Internet nodes might be either connecting a single sensor a or a whole sensor network c to the communication network. Further on, a sensor system might even integrate all
necessary components to act as one single network node, i.e. the sensor system is addressable and accessible within the communication network b.
Figure 5-5: Sensors connected to a Communication Network here: Internet node
Depending on the available addressing options see section 5.2.3, the sensor network appears to users as either a sensor system or a complex form of a sensor. This is the design
decision of the sensor network engineer. Let SN = {S1, S2,…,Sn} be a sensor network with n 0 indicating the number of
sensors in SN. There are the following properties of a sensor network with respect to membership of sensors.
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The membership of a sensor to a sensor network is time-dependent, i.e., sensors may join and leave sensor networks, or formally: SN1 t1
SN1 t2 ≠ Ø with t1 ≠ t2.
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Sensor networks may overlap, i.e., a sensor may be member in more than one sensor network at a given time t, or formally: SN1t
SN2t ≠ Ø.
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Sensors may be moving, i.e. they may change their position. As a consequence of the movement of the sensor it may leave one sensor network SN1 and join another sensor
network SN2, or formally: Si SN1 t1 Si SN2 t2 with t1 ≠ t2. The SensorSA
refers to these sensors as roaming sensors. An example is a sensor node in a wireless sensor network that leaves the reachability zone of a data logger and gets into the
reachability zone of another data logger.
5.5. Service Viewpoint of a Sensor
