# Relationship between UDDI and WSIL

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.
Parent topic: Web Services Inspection Language (WSIL)
Related Concepts
Web services overview
Tools for Web services development
Web Services Inspection Language (WSIL)
Related Tasks
Developing Web services