People we plan to do business with, wants us use the commerce XML technology. I'm not 100% sure, but it looks like something spun out of Microsoft's attempt to control XML business-to-business when XML and B2B were all the rage.
The specification is very verbose, and in my 'flu induced state of mental disfunction, doesn't seem to be very helpful yet. I'll keep going, I'm on page 34, there are another 320 to go.
Alas there doesn't appear to be a cXML module on CPAN, it can't be that popular then. To process these files, I may need to build my own framework...