[3ds max] .axf file format spec?

I am working on a game animation system that relies on .xaf files exported form Max.
It’s easy enough to open and look at the file, which is basically xml, but some of the values are unclear.
is there a spec anywhere for the .xaf file format ?

As far as I can tell, Autodesk hasn’t provided public specifications documentation for the .xaf file format. In the past when I’ve needed to work within .xaf files, I’ve just fumbled my way to a solution. If such a specification exists, I’d love to know about it. : )