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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Data Model(s) for XML 1.0 / XML Devcon / DOM / XSL / Query
 At 11:26 AM 23/02/01 +0000, Sean McGrath wrote: >In the light of recent debate about the intertwingling >of XML specs and the PSVI and Henry Thomsons >excellent keynote at XML Devcon >(http://www.xml.com/pub/a/2001/02/21/xmldevcon1.html). >isn't it time to accept that not specifying formal >post-parse data model(s) for XML 1.0 was a big >mistake? > >Furthermore... ... and so on. Sean makes some good points, particularly that a lot of hair on the DOM is due to the requirement that it support authoring applications. And Henry's slides are damn convincing... maybe all those angle brackets really *are* ephemeral fluff, and the reality is the infoset, or actually, since that doesn't actually help the ordinary programmer very much, the API based on the infoset foundations, and in fact really the whole integrated SDK of which that API is a part... No! <slap slap> Wake up Tim, that was just a bad dream. Here are a few paragraphs I wrote on the subject a couple years back in another conversation, I found them archived over in Dave-Winer-land: It took me years to realise how deep and important the divide is between wanting an SDK and wanting to know the underlying protocol. Too much of our biz can only see one of these realities. I grew up with networked minicomputers and (mostly) Unix, and maybe that's why, in the final analysis, I always want to see the bits on the wire, because in the final analysis, given any programmable device, I can work with them. XML is of course the ultimate expression of that philosophy; it can do a reasonably good job of offering a bits-on-the-wire view of just about anything. During the heydey of client-server I was repeatedly baffled and frustrated by the mind-set, in particular evidence chez Apple and Microsoft, that the only expression of computing reality was a big hairy complicated API with an associated big hairy complicated (and often expensive) SDK. This is not just a Unix-vs-PC thing - the X window system is one of the most extreme examples of the big, hairy, complicated, API (the rumor that they ever actually fully documented the wire protocol is false). And not that this approach is wrong - I'm sitting in front of a Windows box, and three of the windows are X applications running on my big server which off at a distant ISP. These days I write big complicated software in Java, which does a good job of giving you a tractable object model overlaying insanely complex infrastructure. But in a distributed int[ra,er]-net scale app with heterogeneous boxes, there's still no substitute for the bits on the wire. Our profession needs to grow up a bit and actually arrive at a consensus as to when each of these approaches is appropriate, teach it in college, and so on. And another reason that Sean is wrong is that it's taken, in aggregate, in excess of 5 years to shake out the DOM and the infoset, and if we'd held off on XML until we had a consensus data model, we'd still be waiting. At the end of the day Henry is right, you really need the infoset for the same reason that SGML needed groves and property sets, so that you can define higher-level protocols like XPath XSL and XQuery and so on in a nice clean way. So, spec writers need this apparatus. Does the actual *programmer* need to think about it? Usually not; the typical programmer's world-view is either that given by some SDK (with access to SAX and/or the DOM) or in a really heterogeneous system, bits-on-the-wire. Clean abstract enhanced infosets are nice, but they're really hard to load into emacs or IE5 and look at to figure out what's going wrong [which I *always* end up needing to do, maybe others are smart enough to avoid this]. XML was defined at a syntactic level for a reason. Those who want to take another view can, and often it's useful to do so. But let's not claim such a view is truer or deeper in any universal sense. -Tim 
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