The OMML (Office math markup language) specification has been improved in response to the great feedback we received from the ISO reviews. It’s part of the full OpenXML documentation Version 2 and is very handy to have if you’re working with OMML. The full OpenXML documentation itself is also very useful if you’re working more generally with OpenXML.
To get the documentation, click on http://www.ecma-international.org/publications/standards/Ecma-376.htm. Then click on ECMA-376 2nd edition Part1 to start a 50 MB download of the file entitled “ECMA-376, Second Edition, Part 1 - Fundamentals And Markup Language Reference.zip”. Browse the zip file and copy “Part 1: Fundamentals and Markup Language Reference”, a 34 MB pdf file to somewhere convenient on your disk drive. Then open that file with the Adobe Reader. In the left pane of the Reader, click on the Bookmarks icon to navigate this huge file.
To get to the OMML documentation, click on SharedMLs Reference Material, and then on Math. You’ll see three entries, “Table of Contents”, “Elements”, and “Simple Types”. You can click on the “Elements” to see each OMML element referenced. Clicking in turn on one of them, you get the full documentation on that element. Similarly you can investigate the "Simple Types".