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Re: Packaging (was: Embedded style and style wrappers)

From: Bert Bos <Bert.Bos@sophia.inria.fr>
Date: Mon, 27 Sep 1999 02:50:30 +0200 (MET DST)
cc: www-style@w3.org
Message-ID: <Pine.LNX.4.10.9909270112130.6156-100000@meta.inria.fr>
On Sun, 26 Sep 1999, Jelks Cabaniss wrote:

> Bert Bos wrote:
> 
> > > I am interested in the mechanism(s) hinted at in
> > > http://www.w3.org/TR/xml-stylesheet/ (see last paragraph) -- has
> > > there been discussion of some kind of "wrapper" file ...
> >
> > You're not the only one to suggest it. I've heard the same from some
> > W3C members as well (who presumably got it from their customers), so
> > there may well develop a working group in a couple of months. It
> > certainly seems like a good idea to me.
> 
> I just noticed some hints of this.  The newest XML Activity page has this
> paragraph:
> 
> 	In September 1999, we begin the third phase, continuing the
> 	unfinished work from the second phase and introducing a
> 	Working Group on XML Query and plans for a Working Group on
> 	XML Packaging.

That's indeed what I was referring to. I didn't know Dan had already put
it on the Web.

The current moniker for the project is "XML Packaging," because the most
vocal demands came from people on one of the XML working groups, and
because "XML" is the word that sells at the moment. It is evidently not
the intention to package only XML files, and the name of the format itself
(if there will be one) has not been discussed at all yet.

> Also, the new Schema WD[1] gives this as one possible option of locating
> schemas:
> 
> 	The namespace URI of the item to be validated is
> 	dereferenced and yields a package. A standard property
> 	of the package tells what kind of package it is and
> 	hence how to go about getting schema info out of it.
> 	We anticipate a great range of flexibility in the
> 	structuring and content of packages: schemas will
> 	certainly not be the only thing in them. All that
> 	matters to us is that we can get a schema out of them;
> 
> [1]  http://www.w3.org/TR/xmlschema-1/

Note that this is even more speculative than the creation of a packaging
working group. What namespace URIs refer to, if they refer to anything at
all, is heavily debated at the moment. Namespaces were only designed as a
way to create unlimited numbers of unique element & attributes names, not
as a new way of creating links.

Of course, once you have a URI, you can put something at the other end of
it. But there is no consensus, not even a proposal, for knowing in what
cases the namespace URI can be dereferenced or what you may expect to find
at the end of it.

HTTP negotiation may help a bit: when you want the style sheet for a
namespace, you do an HTTP GET with "Accept: text/css", if you want the
schema, you do "Accept: application/xml-schema" (or whatever the MIME type
will be). Problem is that HTTP negotiation is incomplete: you cannot
reliably detect what formats the server can give you, without trying them
one by one. Putting everything in a package and serving the whole thing is
theoretically a solution, but people with limited bandwith are going to
protest...

It's probably better not to expect anything at the end of a namespace URI.
If you want links, XLink (and good old HTML) gives you many more
attributes to play with.


Bert
-- 
  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos/                              W3C/INRIA
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Monday, 27 September 1999 06:42:20 GMT

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