Database Reference
In-Depth Information
The Service Delivery & Utility Manager (SD&UM) combines data streams as
indicated by service workflows within the OpenIoT system in order to deliver the
requested service (typically expressed as an SPARQL query). The SD&UM acts
also as a service metering facility which keeps track of utility metrics for each
service.
The Request De
cation of service
requests to the OpenIoT platform. It comprises a set of services for specifying and
formulating such requests, while also submitting them to the Scheduler. This
component is supported by a GUI (Graphical User Interface).
nition component enables on-the-fly speci
The Request Presentation component is in charge of the visualization of the
outputs of a service. This component selects mash-ups from an appropriate library
in order to facilitate service presentation.
The Con
guration and Monitoring component enables visual management and
con
guration of functionalities over sensors and services that are deployed within
the OpenIoT platform.
2.2 OpenIoT Ontology for Semantic Interoperability and Linked
Data Integration
The OpenIoT ontology represents a universally adopted terminology for the conver-
gence of sensed data with the semantic web. It enhances existing vocabularies for
sensors and Internet Connected Objects (ICOs), with additional concepts relevant to
IoT/cloud integration such as terms to annotate units of measurement, raw sensor
values and points of interest at some speci
c levels of granularity. In particular, the
OpenIoT ontology is extending the W3C SSN ontology, which supports the description
of the physical and processing structure of sensors. Sensors are not constrained to
physical sensing devices: rather a sensor is anything that can estimate/calculate the
value of a phenomenon. Thus, either a device or computational process or a combi-
nation of them could play the role of a sensor. The representation of a sensor in the
ontology links together what it measures (the domain phenomena), the physical sensor
(the device) and its functions and processing (the models).
The OpenoT ontology is available as a single OWL
le, and provides the means for
a semi-automatically generated documentation. Additional annotations have been
added to split the ontology into thematic modules. The implementation of the ontology
and its integration in the OpenIoT architecture are realized through the LSM middle-
ware. LSM transforms the data from virtual sensors into Linked Data stored in RDF
(Resource Description Format), which is de facto queried using SPARQL. In the
context of IoT applications in general and LSM in particular, such queries refer typi-
cally to sensor metadata and historical sensor readings. The SPARQL endpoint of LSM
provides the interface to issue these types of queries. The RDF triple store deployed by
LSM is based on OpenLink Virtuoso and provides a Linked Data query processor that
supports the SPARQL 1.1 standard. While SPARQL queries are executed once over
the entire collection and discarded after the results are produced, queries over Linked
Search WWH ::
Custom Search