Service Descriptions are identified by a service identifier and contain a service
locator that enables accessing the service. Typically they contain further
information like the service output, the type of service or the geographic area for
which the service is provided. The exact contents, structure and representation
depend on design choices taken, which is left open at the Reference
Architecture level. Some examples for service models (structure) and
representations of a service description can be found in [Martín 2012].
The functionalities offered by the IoT Service Resolution FC in brief are:
Discovery functionality finds the IoT Service without any prior
knowledge such as a service identifier. The functionality is used by
providing a service specification as part of a query. What can be queried
based on a service specification depends on what is included in the
service description. As described above, this may include the service
output, the service type and the geographic area for which the service is
provided. The representation of the service specification will also be
linked to the service description, e.g. if the service description is
represented in RDF, a service specification based on SPARQL would be
appropriate; Lookup is a functionality which enables the User to access the service
description having prior knowledge regarding the service identifier; Resolution function resolves the service identifiers to locators through
which the User can contact the Service. A service locators are typically
also included in the service description, the resolution function can be
seen as a convenience function that reduces the amount of information
that has to be communicated, especially if the service description is large
and the contained information is not needed; Other functionalities provided by the IoT Service Resolution FC are the
management of the service descriptions. IoT Services can update, insert
or simply delete the service descriptions from the IoT Service Resolution
FC. It is also possible that these functions are called by the functional
components of the Management FG and not by the IoT Services
themselves.4.2.2.6 Communication
The Communication FG (see Figure 37 below) is an abstraction, modelling the
variety of interaction schemes derived from the many technologies belonging to
IoT systems and providing a common interface to the IoT Service FG.
The Communication FG consists of three functional components:
Hop To Hop Communication; Network Communication; End To End Communication.