"Opaque formats include PostScript, PDF, proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML produced by some word processors for output purposes only."
I cannot believe that the .doc should be considered transparent whereas PostScript or PDF are cited examples of opaque formats.
As far as I know (some of my friends use Open Office, but I don't) it is not so easy to handle .doc files with those free tools than with the "original" MS Word. Sometimes they just cannot open a file. It might not be so easy to "implement the standard".
I think that the "proprietary formats that can be read and edited only by proprietary word processors" allusion was written with MS-Word.doc in mind.
Guillaume Ponce http://www.guillaumeponce.org/