ODF's main opponent has been Microsoft Corp. Because of its market-dominating Office suite, Microsoft formats .doc, .xls and .ppt from Word, Excel and Powerpoint, are the most widely-used, albeit proprietary, formats used by individuals and businesses.

Microsoft is developing a successor format as part of its upcoming Office 2007 which it calls Microsoft Office Open XML. Microsoft says it is licensing Open XML for free to companies and is submitting it to an European standards body, Ecma International, for approval as open standard.

To coalesce around a single standard would hinder innovation, said Jason Matusow, Director of Standards Affairs for Microsoft.

"There are hundreds of industry-specific XML schemas used right now by industries spanning health care, real estate, insurance, finance and others. ODF is yet another XML-based format in the market," he said.

"The ODF format is limited to the features and performance of OpenOffice and StarOffice and would not satisfy most of our Microsoft Office customers today. Yet we will support interoperability with ODF documents as they start to appear and will not oppose its standardization or use by any organization. The richness of competitive choices in the market is good for our customers and for the industry as a whole."