Hey, Just a few brief comments after using it: - <os_type>xen<os_type> is equivalent to <os><type>linux</type></os>, which is pretty confusing. Sounds to me like we should deprecate the latter and move to "xen" everywhere for this. - We have <host><arch>x86_64</arch></host> and <guest><arch name="x86_64"/></guest>. I can see why we did that, but it seems odd to me to have different syntaxes for <arch> depending on its context. - I'm not sure how interesting the stuff in <guest><arch> is ... how were we envisaging these bits being used? - It's a pain to have to parse XML to discover whether e.g. you can run a 64 bit guest. I'd much prefer to see the kind of API I'm using here: http://www.gnome.org/~markmc/code/test-caps.py e.g. caps = cnx.getCapabilities() supports_x86_64 = False for guest in caps.guests: if guest.arch == "x86_64": supports_x86_64 = True Cheers, Mark.