Web services—
Disco
The Web Service Discovery Tool (DISCO) is used to discover the URLs of XML Web Services located on a Web server and saves documents related to each XML service on a local disk. The DISCO takes the URL and discovers and produce publishes discovery documents (.wsdl, .xsd, .disco and .dicomap files) as arguments.
UDDI
Universal Description, Discovery and Integration (UDDI) is a platform independent framework functioning like a directory that provides a mechanism to locate and register web services on the internet.
WSDL
Web Services Description Language (WSDL) is a markup language that describes the web service.
DISCO was initially a Microsoft discovery protocol that was never meant for more than simple document-based lookups. DISCO is ultimately limited by the type and depth of the information that it provides.It is through the discovery process that WCF service clients learn that an WCF service exists and where to find service’s description document.Actually, there is no purpose to it. UDDI is not actually used. It sounded like a good idea at the time, but has turned out not to be usable.
In practice, WCF Service clients learn that an Service exists because someone tells them the URL of the WSDL file.As i know this is not being used any where unless you use Discovery-driven WCF Service.