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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XSD question
 Dare Obasanjo wrote: >The problem lies less with the technology are more with how poorly the spec is organized and the obtuse language in which it is written. This thread is just another example of the annoying tendency for related information being in completely separate parts of the spec with no explicit connection between them. > > Any sufficiently monolithic technology is indistinguishable from spaghetti. Once a large technology is made from sufficiently intertwined parts, there is no way to order an exposition of it such that strongly-connected ideas are always close together. Spaghetti doesn't want to be free. (At least, "no way" to order the exposition with HTML-style pages: maybe WXS needs something more like Nelson's transclusion, where you can pull in fragments (without losing their context) and embed them into running text, without the maintenance penalty of duplicated sections.) Indeed, I think that is a forgotten rationale for XML over SGML: dumbing down an intertwined technology so that it could have a spec straightforward-enough that people could conveniently read it. Schematron is much smaller and more obviously layered, and its spec is pretty crappy. But James Clark did not have to ask a single question to make his recent implementation. (I don't recall that the first two implementations by other people required any questions either.) Why? James may not be the worst programmer in the world. And maybe having a reference implementation helps, IETF fashion (though XSV and Xerces are Open Source and people could refer to them.) But the reason none of thsoe implementers of Schematron have needed to ask many questions (apart from the mess wth <key>) is that Schematron as a technology does not try to do everything. The WXS structures spec is a symptom, not the disease. The Structures spec used to be ordered in a completely different way, and the current order and linking is an improvement. But because the WXS technology is not layered (and because, even where it could be layered, such as the component assembly rules, the validation/traversing rules, and the non-type integrity constraints, it all is stuffed into a single spec), I cannot see how it could be possible to organize most of the structures spec without losing on the swings what you gained on the roundabouts. ISO specs are organized very differently to W3C specs. Much of the work in an ISO specification is done in the definitions section, where terms are defined and kept alphabetically. This means that the specification text proper can use jargon without having to define it, which encourages smaller, pithier paragraphs. Lots of noun phrases rather than subordinate clauses. Verbal subroutines rather than branches and gotos. The tradeoff is that reading ISO specs involves a constant flipping motion, from text to definition and back (hence Goldfarb had the ribbons in his annotated version). This can be quite offputting for people who have not succumbed to the flipping groove, because they look at a paragraph and it is all jargon and they cannot scan backwards to find the definition of the jargon. But it encourages giving a name for everything, rather than clauses. And it allows readers to cut to the chase fairly fast, because they don't need to wade past sections defining terms. I suspect the ISO-esque arrangement also encourages the use of formalisms (I am finding that), because after your concepts are all nicely catalogued in the definition section, information that might complicate a formalism can be stuck as a note in the definitions, and readers know their information should be in one place or the other. That might be another way to factor out information to reduce complexity, but it perhaps is locking the stable door while the horse is still bolted. Cheers Rick Jelliffe 
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