A key feature of the Web services promise is that Web services published with one server can be called from any other client. The ability of each implementation to make use of each others' output is called interoperability. Thus, Web services created with Virtuoso should interoperate smoothly with services created with Microsoft's .NET, Sun's Java, and so on. Interoperable Web services mean that developers and users do not have to think about which programming language or operating system the services are hosted on.

The evolving nature of the SOAP specification, as well as its complexity, leads to differences in SOAP implementations. Unfortunately, these implementation differences decrease interoperability. To counteract this problem, a volunteer group of SOAP application builders has developed a series of interoperability tests.

OpenLink, as a participant in this group, ensures that its SOAP implementation interoperates fully. This means that Virtuoso's SOAP server properly exposes your Web services so they can be used by any client. It also means that Virtuoso can call services published by any compliant provider.

You can view the Round 1 "Interoperability Lab" at www.xmethods.net and the Round 2 at www.whitemesa.com . Please note that OpenLink has no connection with these companies; they are simply places that volunteered to host the testing reference documents on their servers.

The Round 2 tests include base functionality (which duplicates Round 1) as well as more advanced tests labeled "Group B" and "Group C". The WSDL published by OpenLink containing the descriptions of these tests can be found at http://demo.openlinksw.com:8890/Interop/ . This URL will be updated as new interoperability tests are devised.

The SOAP implementation passes all known interoperability tests.