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viewer allows one to see the instances of a concept without browsing through
the tree hierarchy.
When two or more ontologies are opened in DOME, it is possible to cre-
ate mappings between these ontologies. These mappings can later be used for
query rewriting and ontology merging to resolve heterogeneity issues, i.e. in
cases where two business partners use different ontologies to describe the same
domain, these mappings can be used to allow the two partners to communi-
cate.
10.3 Execution Environments
The execution environments of Semantic Web services are complete frame-
works which serve as an architecture to integrate the tasks involved in the
use of Semantic Web services from goal specification to execution. There exist
two WSMO-compliant implementations which follow the conceptual model of
WSMO, to be discussed here.
10.3.1 The Web Service Execution Environment (WSMX)
The amount of human interaction required in the process of finding and using
Web services is a serious limitation on their use. Since WSMO and its WSML
formalization allow Web services to be described semantically, a large portion
of this process can be automated. The Web Service Execution Environment
(WSMX)
15
is a reference implementation of WSMO and is an execution en-
vironment within which semantic descriptions of users' goal and providers'
Web service can be used to
discover
,
compose
,
mediate
,
select
,and
invoke
Web services that match the end user's requirements.
The key aim of WSMX is to define mandatory functional services, decou-
ple their functionalities from one another, and describe components' interfaces
in terms of the offered functionality. One of the design principles of service-
oriented architectures (and Web services in general) is the separation of the
implementation of the service from its externally visible description. Such de-
sign allows the replacement of one service with another as long as the new
service supports a stable interface. Similarly, WSMX does not define services
in terms of their design or implementation details, but only in terms of ex-
pected functionality and their externally visible behavior.
Components
WSMX has a component-based architecture (Fig. 10.8), with each compo-
nent in the architecture performing a discrete piece of functionality. These
units of functionality are drawn together by the formally described execution
semantics of the system.
15
http://www.wsmx.org
.
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