I've had a few folks ask me about other industry standard schemas out there like HR-XML, XBRL, DocBook, etc. The out of the box schemas that are supported are WordprocessingML, SpreadsheetML, and PresenatationML. As I've discussed numerous times though, there is also support for custom defined schema, which means you can take your own schemas and work with them in the applications:
- Create a rich Word document based on your own custom XML (without the need for XSLT)
- Intro to Word XML Part 3: Using Your Own Schema
- Intro to Excel XML Part 3: Displaying your Data
So, if you want to work with another schema, you can take advantage of the custom defined schema support. Using that in combination with the Open XML formats allows you to build some extremely powerful solutions.