Microsoft has won approval for its Office Open XML document format from international standards body ECMA International.

ECMA's General Assembly voted by 20-1 in favour of the standard at a meeting in Zurich on Thursday afternoon, and will now submit the format to the International Organisation for Standardisation (ISO) for its approval. The vote against came from an IBM representative.

A standardised document format will make it easier for competing software companies to develop products that can inter-operate with one another and to edit the same documents. Products meeting the standard could find favour with governments, or other organizations concerned about interoperability.

Inter-operability is vital for the preservation of archive information, according to Adam Farquhar, head of e-architecture at the British Library and a member of the committee that worked on the standard at ECMA. The British Library archives electronic documents, but must deal with whatever format they arrive in. The development of interoperable software tools will make that work easier.

"The level of precision in this standard is unprecedented," Farquhar said. The standard runs to several thousand pages. To help developers digest the standard, the committee has published a 14-page white paper explaining it."The committee put a lot of effort into making the document accessible," Farquhar said.

That accessibility is important if Microsoft is to win developers over to its document format, as the company faces competition in the standards industry just as it does in the software market.

A rival document format, OpenDocument Format (ODF), has already won approval from ISO, and was published as an ISO standard last month. ODF is used by office productivity suites such as OpenOffice.org or Sun's StarOffice, and has gained the support of other companies, including IBM. Government officials in France and the Massachusetts have recommended adoption of ODF as a government standard.

ISO approval "is a critical factor for governments," said Marino Marcich, Managing Director of the ODF Alliance, a body that promotes the OpenDocument Format.

There are still several hurdles to overcome before Microsoft can obtain ISO approval. ECMA has asked that the standard be fast-tracked, a process to which national standards bodies now have about 30 days to object. If no one objects, then ISO sub-committee 34 will spend five or six months examining comments on the standard received from the national standards bodies, and only then will the ISO's Joint Technical Committee 1 vote on the standard.