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Semantic Web Services 181
Goal
Results
Input data
&
preconditions
Composition
Execution
Output data
&
postconditions
Discovery
Domain
knowledge
WS
descriptions
Ontology
Web
Service
registry
Figure 6-11. Web service composition utilization.
6.3.1 Semantic Web Service Discovery
To make the web service accessible for the users, service providers create web service registries.
In these registries the available web service can be found. The initial intend of the
UDDI specification was to work with a UBR (Universal Business Registry), a directory for all
public web services. Later, the UDDI specification recognized the need of multiple registries
and interactions among them. The existence of multiple registries brings new challenges in
web service discovery. The problem is now first found the appropriate registry and then the
suitable web service.
To discover the web service which matches the requirements, semantic based methods are
used. In [78] a scalable, high performance environment for federated web service publication
and discovery among multiple registries method is presented. It is called MWSDI (METEOR-
S Web Services Discovery Infrastructure). It uses an ontology-based approach to organize
registries, enabling semantic classification of all Web services based on domains. MWSDI
makes accessible multiple registries provided by different registry operators.
Next approach based on semantic is presented in [2]. First, it describes an extension to
the UDDI inquiry API specification to enable requesters to specify the required capabilities
of a service. Second, it enhances the service discovery of UDDI by performing semantic
matching and automatic service composition using planning algorithms. In [72] an algorithm
for search in UDDI based on OWL-S is presented. OWL-S is used to semantically describe
web service in terms of capabilities. Using logic inference offered and requested capabilities
are matched to find the relevant web services. The paper includes also a review of other
approaches to web service discovery.