The Concepts of WSMO - Enabling Semantic Web Services: The Web Service Modeling Ontology - page 63

6.2 Web Services
The Web service element of WSMO provides a conceptual model (a meta-
model in MOF terms) for describing, in an explicit and unified manner, all
aspects of a service, including its nonfunctional properties, its functionality,
and the interfaces needed to obtain it. An unambiguous model of services
with a well-defined semantics can be processed and interpreted by computers
without human intervention, enabling the automation of the tasks involved
in the usage of Web services, for example discovery, selection, composition,
mediation, execution, and monitoring.
As observed in [111], the word “service” can be understood in several
different ways, with slightly different meanings: as the provision of value in
some domain, as a software entity able to provide something of value, and as
a means of interacting online with a service provider.
WSMO provides a unified view of a service; the value that the service can
provide is captured by its capability , and the means to interact with the service
provider to request the actual performance of the service, or to negotiate
aspects of its provision, is captured by its interfaces . The software entity that
provides the service is transparent to us. We are concerned only with its style
of interaction and with what other services are used in order to provide the
value described in the capability.
Notice that in WSMO, the interaction with a service can be realized by us-
ing Web services in the WSDL sense. However, we are not restricted to WSDL
for the grounding of services. The elements identified in WSMO are equally
applicable to other underlying technologies, such as Triple Space computing
(Section 12.4). The directions that we have taken for the grounding to WSDL
are described in Section 9.5.
Fig. 6.1. WSMO Web service - general description
The main elements of a service description, depicted in Fig. 6.1, are a
capability, describing the value that the service can provide, and one or more
interfaces, in which the choreography and the orchestration of the service are
described. The choreography specifies how the service achieves its capability