Re: Inheritance in XML
I'm generally not able to track discussions like this, fascinating though they may be, and I make it a firm principle not to become involved in them, so don't expect any further comments from me regarding this one. But catching up on my email backlog just now I see so much good energy being wasted that I can't pass by without contributing a couple of items of information that may save some wheel-spinning out there. First, allow me to vent just a little bit about a common misunderstanding. [Matthew Gertner:] | In last month's Wired, XML made it into the "hype list" with the | comment that we crazy XML types are kidding ourselves because XML will | never fly without well-defined semantics. This gets the "No [expletive deleted], Sherlock" award for excellence in trade press reporting. XML was very carefully designed to have no built-in semantics whatsoever. So considered in isolation, an XML document is found to have... no semantics! What an insight! And we can go further: to give semantics to this thing that was designed to have no semantics we have to have... it's coming to me, wait a minute... yes! We have to supply something else that *does* provide the semantics! Wow! Pulitzer prize time for sure. Here are some examples of things that can provide semantics for XML documents: * Scripts or programs. Especially Java programs. :-) * Prose descriptions (if you said "DTDs" you are confused, but understandably so; a lot of good people have been confused about this before you). The namespace specification provides a standard way to associate prose descriptions and other bearers of semantic information with classes of XML documents. * Stylesheeets. Especially XSL stylesheets, which are even as we speak being defined by a very active W3C XSL WG. This is why you will want to look carefully at the first XSL working draft expected out in July, because XSL will provide what is intended to be the most powerful standardized high-level way to associate presentational semantics with XML documents in publishing environments. Watch this space: http://www.w3.org/Style/XSL So people who think that there is something missing from XML are by and large simply unaware that it was not intended to be used by itself and that the other pieces are on their way. (There's XLink, too.) This has all been made abundantly clear in every W3C statement about the XML activity for the last year and a half, but it's to be expected that a lot of folks just won't bother to pay attention to stuff like that. Now let's turn to the chief concern of this thread. After a number of excellent observations about the need for a schema language for XML documents and the considerations that have to go into the specification of such a thing, Matthew asks the following question: | More tricky than any of these technical issues is the question of | what, if anything, could be done to promote a mechanism of this | sort. Obviously this would require a change to the XML spec as | well as modification to all existing tools which process DTDs, so | it's a pretty big deal. I wonder if anyone besides me thinks that | a simple mechanism like this would make sense. If so, is there | any room in the XML standards process to discuss a change of this | type at some point in the future (certainly not for XML 1.0)? The answer is, Yes, there are other people who think that it would make sense to design an XML schema mechanism to handle issues like what has been called "inheritance" in this discussion (not to mention good old-fashioned data typing). The workings of a W3C committee can be made public only at the discretion of the chair of the committee, so I will put on my official XML WG Chairman hat and reveal unto ye that the XML WG has officially requested that the job of defining a schema language for XML documents be added to its charter. If approved by the W3C Director, this work would certainly involve a consideration of most of the issues raised in this discussion and would include a close look not only at XML Data but also at other proposed solutions to the same problem. Jon xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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