The Web Services Inspection Language (WSIL) and the Universal Description,
Discovery, and Integration (UDDI) specification both address issues related
to Web service discovery. However, each specification takes a different approach
to the discovery of Web services. The two specifications can be used separately
or jointly; searching with WSIL can result in finding items in UDDI.
The UDDI specification addresses Web service discovery through the use
of a centralized model. One or more repositories are created to house information
about businesses and the services they offer. Requests and updates pertaining
to the service and business related information are issued directly against
the repositories. In addition, UDDI prescribes a specific format for a portion
of the stored description information and, to facilitate advanced (focused)
searching, assumes that other description information will be stored and registered
within the system as well.
UDDI systems facilitate focused discovery patterns since these systems
are based on organized repositories that provide advanced searching capabilities.
This helps requestors locate potential communication partners. In order to
provide advanced functionality, however, UDDI requires the deployment and
maintenance of a certain amount of infrastructure, thus increasing the cost
of operation. In addition, unless the service descriptions are stored only
within UDDI, there is a cost associated with keeping the different versions
synchronized.
The WSIL specification relies on a completely distributed model for providing
service-related information. The service descriptions can be stored at any
location, and requests to retrieve the information are generally made directly
to the entities that are offering the services. The WSIL specification does
not stipulate any particular format for the service information. It relies
on other standards, including UDDI, to define the description formats. The
WSIL specification also relies on existing Web technologies and infrastructure
to provide mechanisms for publishing and retrieving its documents.
WSIL provides the ability to disseminate service-related information through
existing protocols directly from the point at which the service is being offered.
This enables focused discovery to be performed on a single target; however,
because of its decentralized and distributed model, WSIL is not a good mechanism
for executing focused discovery if the communication partner is unknown.
The UDDI and WSIL specifications should be viewed as complementary technologies
to be used either together or separately depending on the situation. For example,
a UDDI repository could be populated based on the results found when performing
a search for WSIL documents. Likewise, a UDDI repository may itself be discovered
when a requester retrieves a WSIL document that references an entry in the
repository. In environments where the advanced functionality afforded by UDDI
is not required and where constraints do not allow for its deployment, the
WSIL mechanism may provide all of the capabilities that are needed. In situations
where data needs to be centrally managed, a UDDI solution alone may provide
the best fit. The UDDI and WSIL specifications should not be viewed as mutually
exclusive.
Note: Both UDDI and WSIL contain only references to WSDL - they do not contain
the WSDL documents themselves.
