[nullbyte808]

Yeah but those are open standards, where as Microsoft is the only one with true knowledge of its XML.

[wvenable]

You know you're referring to ECMA-376 and ISO/IEC 29500?

[mdaniel]

In OP's defense, is there a freely available reference implementation of that standard? I know that LibreOffice certainly tries but I'd guess theirs is closer to a reverse engineered than reference impl