International Symposium on Software Composition

Office Open XML

Office Open XML (also informally known as OOXML or Microsoft Open XML (MOX)) is a zipped, XML-based file format developed by Microsoft for representing spreadsheets, charts, presentations and word processing documents. The format was initially standardized by Ecma (as ECMA-376), and by the ISO and IEC (as ISO/IEC 29500) in later versions.

Microsoft announced in November 2005 that it would co-sponsor standardization of the new version of their XML-based formats through Ecma International as "Office Open XML". The presentation was made to Ecma by Microsoft's Jean Paoli and Isabelle Valet-Harper.

This standard was then fast-tracked in the Joint Technical Committee 1 of ISO and IEC. After initially failing to pass, an amended version of the format received the necessary votes for approval as an ISO/IEC Standard as the result of a JTC 1 fast-tracking standardization process that concluded in April 2008. The resulting four-part International Standard (designated ISO/IEC 29500:2008) was published in November 2008 and can be downloaded from the ITTF. A technically equivalent set of texts is published by Ecma as ECMA-376 Office Open XML File Formatsó2nd edition (December 2008); they can be downloaded from their web site.

The same InfoWorld article reported that IBM (which supports the ODF format) threatened to leave standards bodies that it said allow dominant corporations like Microsoft to wield undue influence. The article further says that Microsoft was accused of co-opting the standardization process by leaning on countries to ensure that it got enough votes at the ISO for Office Open XML to pass, although it does not specify exactly who accused Microsoft.

This is limited to applications which do not deviate from the ISO/IEC 29500:2008 or Ecma-376 standard and to parties that do not "file, maintain or voluntarily participate in a patent infringement lawsuit against a Microsoft implementation of such Covered Specification". The Open Specification Promise was included in documents submitted to ISO/IEC in support of the ECMA-376 fast-track submission. Ecma International asserted that, "The OSP enables both open source and commercial software to implement [the specification]".

The ISO/IEC standard is structured into four parts: Parts 1, 2 and 3 are independent standards; for example, Part 2, specifying Open Packaging Conventions, is used by other file formats including XPS and Design Web Format. Part 4 is to be read as a modification to Part 1, which it requires.

The intent of the changes from ECMA-376 1st Edition to ISO/IEC 29500:2008 was that a valid ECMA-376 document would also be a valid ISO 29500 Transitional document; however, at least one change introduced at the BRM-refusing to allow further values for xsd:boolean-had the effect of breaking backwards-compatibility for most documents. A fix for this had been suggested to ISO/IEC JTC1/SC34/WG4, and was approved in June 2009 as a recommendation for the first revision to Office Open XML.

Applications capable of reading documents compliant to ECMA-376 Edition 1 would regard ISO/IEC 29500-4 Transitional documents containing ISO 8601 dates as corrupt.

Starting with Microsoft Office 2007, the Office Open XML file formats have become the default file format of Microsoft Office. However, due to the changes introduced in the Office Open XML standard, Office 2007 is not wholly in compliance with ISO/IEC 29500:2008. Office 2010 includes support for opening documents of the ISO/IEC 29500:2008-compliant version of Office Open XML, but it can only save documents conforming to the transitional, not the strict, schemas of the specification. Note that the intent of the ISO/IEC is to allow the removal of the transitional variant from the ISO/IEC 29500 standard.