Semantics and Sensors
As networks of sensors become more commonplace there is a greater need for the management and querying of these sensor networks to be assisted by standards and computer reasoning. The OGC's Sensor Web Enablement activities have produced a services-based architecture and standards, including four languages for describing sensors, their capabilities and measurements, and other relevant aspects of environments involving multiple heterogeneous sensors. These standards assist, amongst other things, in cataloguing sensors and understanding the processes by which measurements are reached, as well as limited interoperability and data exchange based on XML and standardized tags. However, they do not provide semantic interoperability and do not provide a basis for reasoning that can ease development of advanced applications.
Ontologies and other semantic technologies can be key enabling technologies for sensor networks because they can improve semantic interoperability and integration, as well as facilitate reasoning, classification and other types of assurance and automation not addressed in the OGC standards. A semantic sensor network will allow the network, its sensors and the resulting data to be organised, installed and managed, queried, understood and controlled through high-level specifications. Sensors are different to other technologies, such as services in service-oriented architectures, because of the event based nature of sensors and sensor networks and the temporal and spatial relationships that need to be considered. Further, when reasoning about sensors, complex physical constraints such as limited power availability, limited memory, variable data quality, and loose connectivity need to be taken into account. When these constraints are formally represented in an ontology, inference techniques are more readily applied.
The Incubator Group Activity (XG)
Given the current state of the overall subject of sensor ontologies and the different ways to annotate those, it became clear that the best approach would be to create an Incubator group, which provides an opportunity to share perspectives on the topic with all the advantages noted by the W3C. Once the group was launched, the group's Charter was posted with all the details regarding the group's assignments, rules, and deliverables. Among the instructions, SSN-XG members were reminded that membership conditions include patent disclosure obligations as set out in Section 6 of the W3C Patent Policy and of their goal to produce work that can be implemented on a Royalty Free basis, as defined in the W3C Patent Policy.