This seems innocuous enough, but some people claim that by doing so, were allowing proprietary formats to rule the day once again; all of the transparency and nifty markup tools that XML gives you go away, and Evil Vendors will smite us with their Terrible, Proprietary Formats.Which, I say, is hogwash. - Mark Nottingham I here what Mark's saying, but you know, there's not much in the history of our industry to back him up. Quite the opposite. We don't even need BeEvil type vendors for this to be an issue - we just need people who don't think clearly about how to inspect encoded goo in a working system running around designing said systems. The real question here and boy, is this the elephant in the virtual room is whether XML is the best way to model data. Compared to, I dunno- Base64? XML is not for data modelling; it's for marking up. You need a data model model to model data - XML doesn't have one of those and probably doesn't need one (in fact I'm sure it doesn't - RDF/XML, WXS, anyone? No?). Nah, if that's is an elephant, it's white. The elephant in my room is whether XML packaging over all other considerations is a good idea. Mark mentions this, but almost as an aside. To be specific, must everything go under the root element? XML packaging is currently Atom's biggest technical headache, although people aren't coming out and saying it just yet. Sometimes it seems that putting binary in XML is like putting beer in an envelope. SOAP with Attachments was apparently a "horrible mess", as Mark puts it, but I've never heard anything more specific than that. Was it more horrible than multipart MIME? Will XOP be less horrible?...