WSDL: Given a Web Service, it would be nice to have a standard way to
document what messages the Web Service accepts and generates—that is, to
document the Web Service contract. A standard language makes it easy for
developers and developer tools to create and interpret contracts. The WSDL
(Web Services Description Language) is an XML-based contract language jointly
developed by Microsoft and IBM

DISCO: Developers will need some way to discover Web Services. The DISCO
(Discovery of Web Services) provides a way to discover and retrieve WSDL
description of services on remote machines

UDDI: Universal Description, Discovery, and Integration (UDDI) specifies a
mechanism for Web Service providers to advertise the existance of their Web
Services

Regards
JIGNESH