The International Organization for Standardization (ISO) has published the Office Open XML (OOXML). OOXML is a file format for representing spreadsheets, charts, presentations and word processing documents. An Office Open XML document file contains mainly XML based files compressed within a zip package. The announcement was made on the ISO news release, Publication of ISO/IEC 29500:2008, Information technology - Document description and processing languages - Office Open XML file formats.
The documentation for Office Open XML (OOXML) runs 7,228 pages and can be ordered on CD from the ISO for 342 Swiss francs ($285). The specification is named ISO/IEC DIS 29500:2008.
The specification was approved as an international standard this past April.
Microsoft uses a version of OOXML in its 2007 Office System. Future software products would adhere to the ISO-approved OOXML specification.
You can learn more about how your software can support the Open Office XML standard at OpenXML Developer. You'll find the lastest community technology preview that supports the Office Open XML standard at Open XML Format SDK 2.0.
Check out Doug Mahugh's blog for the latest in interoperability of Office System.