Re: [nsMediaType-3] Principles and corner cases

On Fri, 2002-02-01 at 19:48, Tim Berners-Lee wrote:
> I would like us to state the stronger case that in any case,
> the meaning of XML is always dependent on the parental context.
> Otherwise, we manacle the design of new langauges.

I would like to warn that insisting "the meaning of XML is always
dependent on the parental context" is itself a manacle on the design of
new languages.  

XSLT is only one example where the contents of a document may have
"meaning" regardless of the context containing them.  I've created a
variety of XML vocabularies which have no concern or limited concern for
context and which are designed to be mixable, and I hardly think I'm
alone in this.

Parental context is useful _some of the time_.  Insisting that it is
useful (or not useful) in all cases is simply not going to be an
accurate claim.  (There are even people who find XML's insistence on a
single root element to be a fundamental flaw.)

> > P4. The namespace of the root element of an XML resource
> > has a special status, if only because it provides the
> > outermost level of context.
> Practically, when a document is turned into an object,
> it determines what sort of an object.  In other words, (whether or not you
> have  XSLT inside it) you will always get a graphic object.
> You can expect it to be able to render itself.

First, not all documents are turned into objects. I can see where that
notion might come from in a browser context, but it doesn't apply to all
potential use cases.

Second, I wouldn't expect an SVG document containing XSLT to render
itself without the aid of an XSLT processor, which may or may not be
present and/or compatible with the particular SVG processor's
expectations.  "Getting" a graphic object is a pretty complex process in
this case.

> To do anything else leads, as far as I can see, to total chaos.
> The supreme court will have to sit every time we need to figure
> out whether it is an SVG, XSLT, or Conditional document.

I see no chaos, and no need to impose the order you seem inclined to
impose.  The supreme court needn't figure out whether documents are
"SVG, XSLT, or Conditional".  Programs can do their best to determine
such things, or humans can do their best to help them.  
Adding a file extension of ".xsl" to documents meant to be XSLT and
".svg" to documents meant to be SVG is a very simple way to deal with
these cases and make them amenable to automated processing.  (If you
don't like the notion of file extensions, assigning MIME Media Types
will do as well, and are likely driven off the extensions anyway.)

Simon St.Laurent
Ring around the content, a pocket full of brackets
Errors, errors, all fall down!

Received on Sunday, 3 February 2002 21:17:47 UTC