In most scenarios the sensors are implemented as devices. The class ssn:Device describes an abstract device and inherits all the properties of the class ssn:System (subcomponents, platform to which a system is attached, deployment in which a system participates, operating and survival range). All physical sensor devices are represented by the class ssn:SensingDevice in the ontology. Instances of this class possess all properties of the classes ssn:Sensor and ssn:Device.
This module only has one class ssn:Device which lies in an intermediate position in the class hierarchy as shown in Figure 5.25. Generally, instance of ssn:SensorDevice will be created. An example of device is included in the Measuring module documentation and is used in the MeasuringCapability module documentation to illustrate how a ssn:MeasurementCapability can be specified.