Simple Object Access Protocol (SOAP) provides a common messaging format for web services. SOAP enables objects not known to one another to exchange messages. SOAP uses an XML-based data encoding format and HTTP to transport messages. SOAP is independent of both the programming language and the operational platform, and it does not require any specific technology at its endpoints.
ebXML (Electronic Business using eXtensible Markup Language) is a set of specifications that enables enterprises to conduct business over the Internet. OASIS (Organization for the Advancement of Structured Information Standards) controls the ebXML specifications. Similar to a telephone system's yellow pages, an ebXML registry enables providers to register their services and requestors to find services. Once a requestor finds a service, the registry has no more role to play between the requestor and the provider.
Web Services Description Language (WSDL) defines a standard way to specify the details of a web service. It is a general-purpose XML schema that can specify details of web service interfaces, bindings, and other deployment details. By having such a standard way to specify details of a service, clients who have no prior knowledge of a web service can use it.