Page xii of the Part1 of the OOXML specifications mentions the following:
The goal is to enable the implementation of the Office Open XML formats by the widest set of tools and platforms, fostering interoperability across office productivity applications and line-of-business systems, as well as to support and strengthen document archival and preservation, all in a way that is fully compatible with the large existing investments in Microsoft Office documents.
Why does Office Open XML look like previous Office formats, wrapped in angle brackets?
It works best this way. Office Open XML needs to be as compatible as possible with older versions of Microsoft Office's file formats, and the best way to do that is to use a format with a similar design model. Since there are several million Office documents for every developer that's ever worked on Microsoft Office, the only practical way of ensuring compatibility with that huge corpus is by making cautious, incremental changes.
Business Presentation of ECMA
Office Open XML Document Formats
• Designed to represent all information of .doc, .ppt and .xls in XML
• Default file format for Office 12
• Proposals for complementary or additional technology are considered for the evolution of the standard, under the provison of insured backward compatibility.
What's backwards compatibility first of all? For everyone in the world, except for Microsoft, file backwards compatibility means that product in version N can work seamlessly with files produced by the product in version N+1. For Microsoft however, it's the opposite, backwards compatibility means that product version N+1 can work seamlessly with files produced by the product in version N. By "work seamlessly" is meant no visible degradation, no noticeable loss in functionality.
Cmp. FFII's <no>OOXML petition:
8. This standard proposal was not created by bringing together the experience and expertise of all interested parties (such as the producers, sellers, buyers, users and regulators), but by Microsoft alone.
Despite all the cover-up Ecma described a single vendor policy as the essence of the Office Open XML format as proposed to the International Standards Organisation (ISO) fast-track procedure. FFII urged ISO members to deny the fast-track route for OOXML as this procedure makes it more difficult to improve a premature format.
Scenario: Failure of ISO Approval
We still have the ECMA standard developed for a single vendor.
Scenario: ISO Adoption of OOXML
A single vendor format becomes an international standard. The market gets no gain from an ISO approval of a single vendor format.