Sun Microsystems Inc has rallied a handful of ISVs to the newest web services specification, potentially aggravating partisan splits within the industry.

Palo Alto, California-based Sun is backing the Web Service Choreography Interface (WSCI), to describe and manage flow of elements inside a web service.

Missing from the initial line-up, though, are Microsoft and IBM. Their omission adds to a growing perception of partisanship over development of web services specifications, blighting the original vision of web services for seamless interoperability.

IBM and Redmond, Washington-based Microsoft have participated in development of a number of key web services specifications, such as Simple Object Access Protocol (SOAP).

Meanwhile, Sun - it seems - was deliberately omitted from foundation of the Web Services Interoperability (WS-I) organization, co-founded by IBM and Microsoft, with the approval of Bill Gates.

Susy Struble, Sun XML industry initiative manager, said IBM and Microsoft were "aware" of WSCI and that they had seen the specification. She did not say, though, whether the companies had been invited to join this effort.

Neither IBM or Microsoft were available for comment.

WSCI will be offered to the industry free of royalties - a further point of contention. Controversy was recently stirred when IBM notified the Organization for Advancement of Structured Information Standards (OASIS) it owned patents over elements of the Sun-backed electronic business XML (ebXML).

Struble said it didn't matter if vendors actually charged royalties, but that their mere existence created uncertainty for organizations building web services. "We are genuinely concerned. It creates pressure on the developer and the user," she said.

WSCI is based on WSDL but designed to overcome the description language's limitations. Sun said WSDL and other specifications are suitable for the retrieval of simple information, like stock quotes, but do not support more complex transactions such as airline ticketing systems.

An airline ticketing system, for example, must deal with booking and payment transactions, and handle internal faults and recovery. WSCI is designed to enable this process by describing the flow of messages exchanged by a web service in a particular process and enable message exchange among interacting web services.

It's an approach taken by San Jose, California-based BEA. The company allows developers to build these so-called "conversational" web service elements in WebLogic Workshop - announced this week.

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