- From: Rick Jelliffe <rjelliffe@allette.com.au>
- Date: Fri, 22 May 2009 00:17:50 +1000
- To: www-tag@w3.org
Mukul Gandhi wrote: > I agree. But we shouldn't make things so simple, that we do not meet > the requirements of the stakeholders. We already have Lite Schema > technologies, like RELAX NG or Schematron. Why do you want to impose > everything from there onto XSD? > Err, so that XSD users (including me) can get our jobs done without all the mucking around? To increase interoperability? To claw back XSD from the serial inflators? To try to help XML get back on its small-is-beautiful foundations? To make sure that core XML technologies are small enough that small FOSS developers can implement them (with code and functionality that is simple enough for Eric Raymond's million eyeballs effect to come into play for maintenance.) Take your pick! Last week, a colleague of mine implemented Schematron (using CSS selectors) for browser-side validation. It took him 300 lines of JavaScript code (it doesn't use XSLT). And it is more powerful in the constraints it can validate than XSD. And people can understand its validation messages. And the schemas are compact. I don't know if the XSD WG really realizes how low XSD's bang-per-buck ratio actually is. There is an incredibly high price being paid (in complexity and its flow-ons of spec complexity, implementation incompleteness, consequent random interoperability, and subsequent abandonment of using XSD for actual validation) for the niche features and monolithic construction of XSD. > I like the type system of XSD (the concepts of simple and complex > types) very appealing. > But complex type derivation doesn't work. You often have to change the base schema. But gee it looks scientific. > I can point to one specific technology (NVDL, http://www.nvdl.org/) > which makes heterogeneous Schema technologies to coexist in a single > application. > Yes, I worked on its development. It is pretty good, and was designed to play with XSD. Has the XSD WG ever considered it? Have they ever considered any external layered technology? > On the hindsight, from your arguments so far, I can judge, you are in > absolute conflict with the goals of the XSD WG. You want to > significantly change the core of XSD. > But XSD currently does not have a core, or at least, looking for it is like looking for the core of a plate of spaghetti. Certainly I do differ from what I think is the viewpoint of many on the XSD WG: I don't see type derivation as the substance of XSD, but just as an additional feature for organization and modelling, related to "how" constraints are organized and modeled. A useful layer in some cases, but severable and otiose and bloating as an explicit facility for an XSD Lite (and indeed, unnecessary conceptually for XSD Lite.) Complex type derivation is no more inseparable from XSD than <import> is. The grammar and facets and XPaths are the things that express the constraints. The basic mechanisms of referencing types is all that is needed. > You were free to propose any requirements to XSD, when the whole XSD > processes started (1.0 or 1.1). But you are suggesting to hold XSD > 1.1, when we are almost complete, and XSD 1.0 users are waiting for > XSD 1.1 to become REC. > I first stated my preference for uncomplicatedness to the XML Schema WG ten years and 14 days ago: "This kind of complication...rings lots of alarm bells with me." (The particular issues changed, of course.) Trawling through the archive I note Henry's comment: from Jan 2000* in response to a couple of calls for a more layered approach to XSD: "The next draft will have a much more layered 'look-and-feel', I promise." "Feature bloat is always a temptation to be guarded against: but remember Occam: "Do not multiply entities _beyond necessity_". Each of the things you identify in your list of 'not needed' is on someone else's 'must have' list. The WG has done its best to balance a wide range of requirements and use cases against complexity, scale and implementability. After ten years, it is time to make good on that promise! (I am not picking on Henry, nor trying to do some long-term bait-and-switch: but I think his comment was typical of what we have heard from the start and no different from what we get today.) Sorry, but saying, in effect, "we have no real metric for stopping adding features" is no reason for not having a profile: indeed, the bloated standards generated by that approach surely must need a profile in short measure. Cheers Rick Jelliffe * http://lists.w3.org/Archives/Public/www-xml-schema-comments/2000JanMar/0063.html
Received on Thursday, 21 May 2009 14:18:38 UTC