The phone book analogy for UDDI is so appropriate that the UDDI designers actually use phone book terminology to refer to the kinds of data stored in UDDI. Basically, there are three “roles” for UDDI data:
White pages contain technical contact information and addresses so that potential Web service customers know how to reach the publishers to do any up-front negotiations or to obtain technical support.
Yellow pages contain information about the various services available from businesses. If you want a kind of service but don't know of any specific companies, you search the yellow pages.
Green pages contain technical information about the Web service itself, and may even include the WSDL description of the service.
These roles are really ...