Inheritance in XML

[Matthew Gertner]

Jon,

Thanks for the info. This is interesting stuff indeed. BTW: I hope you are
wrong about good energy being wasted. I at least feel I learned a lot from
this discussion.

Cheers,

Matthew

-----Original Message-----
From: Jon Bosak <Jon.Bosak at eng.Sun.COM>
To: xml-dev at ic.ac.uk <xml-dev at ic.ac.uk>
Date: Thursday, April 23, 1998 6:31 AM
Subject: 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 Shit, 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



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