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1. Data-level mediation: mediation between heterogeneous data sources
and transfer protocols; within ontology-based frameworks such as WSMO,
this is mainly concerned with ontology integration.
2. Functional-level mediation: mediation between heterogeneous func-
tionalities requested and provided; in WSMO, this relates to capability
descriptions of goals and Web services that are similar but do not match
precisely.
3. Process-level mediation: mediation between heterogeneous communi-
cation protocols and business processes; in WSMO, this relates mainly to
choreographies of Web services that ought to interact with the mismatch
handling on the business logic level of Web services (which is related to
the orchestration of Web Services).
WSMO mediators realize a mediation-orientated architecture for Semantic
Web services, thereby providing an infrastructure for handling heterogeneities
that may possibly arise between WSMO components and realizing the design
concepts of strong decoupling and strong mediation. We explain the WSMO
mediation architecture in further detail in Section 9.3.
6.4.1 Description of a Mediator
A WSMO mediator connects WSMO components and resolves mismatches
between them. The following gives the general definition:
Class mediator
hasNonFunctionalProperty type nonFunctionalProperty
importsOntology type ontology
hasSource type
{
ontology, goal , webService, mediator
}
hasTarget type
}
hasMediationService type { webService, goal , wwMediator }
{
ontology, goal , webService, mediator
Nonfunctional properties. As a mediator can be provided as a service, the
same nonfunctional properties as for Web services are used (see Section 6.2
for what these nonfunctional properties consist of).
Imported ontologies. Imported ontologies are used to import the explicit,
formal vocabulary used in the specification of a mediator; they play the
same role as in the case of ontologies or any other element defined by
WSMO.
Source. The source component of a mediator defines the resources for which
heterogeneities are resolved; a mediator can have several source compo-
nents.
Target. The target component of a mediator is the component that receives
the mediated source components.
Mediation service. The mediation service defines the mediation facility
applied for resolving mismatches. This can be defined in various ways:
directly (i.e. explicitly linking to a mediation service); via a goal that
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