Open XML, a data format used in Microsoft Corp.'s Office software line has been approved as an international standard — a move aimed at preserving access to documents created with the package for years to come.

Companies and governments had expressed concern that documents created with Microsoft's proprietary technology might be impossible to read at some point in the future if Microsoft shifted to a format incompatible with current versions.

The groundswell threatened to hurt demand for Microsoft's highly profitable Office products, which include such programs as Word and Excel. So last year, Microsoft proposed making its "Open XML" format — which is the default format in its newly released Office 2007 line of software — an international standard that could be licensed for free.

That would allow anyone to build products that access information stored in Office documents, similar to how Adobe Systems Inc. lets outside developers create programs that work with Adobe's PDF.

Microsoft submitted the proposal with Ecma International, a Geneva-based industry group that establishes technical standards, and got backing from other players, including rival Apple Computer Inc. Ecma International announced Thursday its approval of Office Open XML as a standard, touting the step as vital for document creation and archiving.

"Hopefully this will allow some of the supposed conflict to die down," said Alan Yates, general manager for information-worker strategy at Microsoft. "Now that OpenXML is an open international standard, we think that people will essentially have much greater trust that it's around for the long term."