Open Geospatial Consortium Sensor Observation Research Articles

Semantic integration of wireless sensor networks into open geospatial consortium sensor observation service to access and share environmental monitoring systems

Integrating heterogeneous wireless sensor networks with the Sensor Web will increase the utilisation of sensors and facilitate the sharing of their observations in environmental monitoring. A centralised framework was introduced for the semantic integration of heterogeneous sensors and their observations into open geospatial consortium sensor observation services (SOSs). An ontology called 1451 ontology was created following IEEE 1451 standards. The 1451 ontology not only describes the sensor properties and observations, but it also specifies the communication interface and protocol. Another ontology called SOS data ontology was also created to represent the feature of interest of the SOS. A matching rule was established to map the two created ontologies with the aim of creating a uniform collaboration of sensors scattered worldwide through the Sensor web. A case study of soil temperature sensor and three-dimensional digital compass shows that sensors can actively register themselves and insert observations into the SOS through the developed programme embedded in terminal devices and the ontology matching module of the web. A semantic link between the IEEE 1451 specifications and the SOS operations will enable the spatially distributed sensors to publish their information in a unified way and to work cooperatively in real-time for significant environmental monitoring.

A sensor data mediator bridging the OGC Sensor Observation Service (SOS) and the OASIS Open Data Protocol (OData)

The World-Wide Sensor Web is generating tremendous amount of real-time sensor data streams and will enable scientists to observe phenomena that are previously unobservable. As the concept of sensor web is to connect all the sensors and their data to achieve shared goals, improving the openness and accessibility of sensor data is important. The Open Geospatial Consortium Sensor Observation Service (SOS) defines standard web service protocols for sharing sensor data online in an interoperable manner. However, SOS has a relatively weak ecosystem, which makes it difficult to build and consume, and it only supports predefined queries. On the other hand, the OASIS1 Open Data Protocol (OData) has a strong ecosystem and flexible query functions. But the soft-typing approach of OData requires it to have a commonly agreed data model to be interoperable. As we argue that the two standards can benefit from each other, we propose a sensor data mediator solution and define an SOS entity data model for OData (SOS-OData) to bridge these two standards. Our prototype demonstrates that the proposed system can convert between existing SOS and SOS-OData services. As a result, we not only can consume SOS data with the flexible OData query functions, but can also easily build an SOS-compliant service with the strong OData ecosystem. We argue that the bridging between these two standards would consequently lead us to the vision of open data for sensor web.

A RESTful proxy and data model for linked sensor data

The vision of a Digital Earth calls for more dynamic information systems, new sources of information, and stronger capabilities for their integration. Sensor networks have been identified as a major information source for the Digital Earth, while Semantic Web technologies have been proposed to facilitate integration. So far, sensor data are stored and published using the Observations & Measurements standard of the Open Geospatial Consortium (OGC) as data model. With the advent of Volunteered Geographic Information and the Semantic Sensor Web, work on an ontological model gained importance within Sensor Web Enablement (SWE). In contrast to data models, an ontological approach abstracts from implementation details by focusing on modeling the physical world from the perspective of a particular domain. Ontologies restrict the interpretation of vocabularies toward their intended meaning. The ongoing paradigm shift to Linked Sensor Data complements this attempt. Two questions have to be addressed: (1) how to refer to changing and frequently updated data sets using Uniform Resource Identifiers, and (2) how to establish meaningful links between those data sets, that is, observations, sensors, features of interest, and observed properties? In this paper, we present a Linked Data model and a RESTful proxy for OGC's Sensor Observation Service to improve integration and inter-linkage of observation data for the Digital Earth.