Proposal Critique - XML DTDs to XML docs

[Simon St.Laurent]

>I am not yet convinced that
>structural inclusion (e.g. get that tree from that document and place it
>*here*) can completely and conveniently replace XML/SGML's text
>substitution model. I'm ready to be convinced, however. Once XLink is done
>and widely implemented, we will have an opportunity to pit the two methods
>head to head against each other, and the market will decide.

I think letting the market decide here is a wise idea, but I remain concerned 
that XLink hasn't yet stepped up to the challenge.  Given the variety of 
interpretations surrounding the behavior of EMBED, and the number of people 
who told me last time I asked that EMBED _wasn't_ about text substitution, I'm 
not sure the market will get a chance to decide.  I hope this is made explicit 
by the time the standard reaches stability.

>I believe that by the time RDF and XML-Data are done, there should be
>little overlap between them. RDF schemata constrain relationships between
>elements of particular types. XML-Data constrains where they can occur. So
>it there is still a question about managing multiple files and layers, but
>should NOT be a question of duplication of services.
>
>I try to think of the situation as analogous to stylesheets.

I must admit I remain skeptical; RDF and XML-Data seem to want to do too much 
of the same thing at this point.  It doesn't help that they look radically 
different.  I don't mind telling people to use one or the other, but using 
both seems like a lot.  Again, I hope this is cleared up by the time the 
standards reach stability.

The analogy to stylesheets unfortunately makes me wonder if we're going to see 
documents using both CSS and XSL, leaving applications to puzzle out which to 
use and how/if they should interact.  

A uniform standard defining how resources (schemas, DTDs, stylesheets, 
extended link documents, etc.) should be linked to documents and with what 
priority would go a long way toward easing my concerns.  The current soup of 
PIs, DOCTYPE, and XLink elements is messy at best.

>Well, there are no more conservatives anymore. ISO seems willing to go far
>beyond what you or I am proposing. As I understand it, they are moving to
>a situation where DTDs can be in *any notation* whatsoever. 

Looks like I'm turning into the conservative.  *Any notation* sounds like an 
expansion into the world of 'how many options can you conceivably overload 
this system with?'  One of the most important things I liked about XML was its 
insistence on single mechanisms with no options.  It might make sense to break 
validation and schema issues into a 'family' of standards, connected by the 
uniform linking standard mentioned above, but at this point I think we have 
plenty of chaos.

>I wasn't asking about syntax, but about actual specifications. Should the
>validation language be specified in the same standards document as the
>language syntax? I think that we agree that it should not.

Completely right.  This opens the way to a family of standards and hopefully 
will reduce the number of bullets whizzing by.

>Well, I think that this is what XML-Data is about, but it is only a rough
>sketch. I also think that the W3C is supposed to create a working group
>that will address these sorts of issues. We could work out a concrete
>proposal in this mailing list, or offline

I'd like to see that rough sketch grow into a usable set of standards.  I 
wrote the 'Representation' proposal to get some public discussion started, and 
that seems to have succeeded.  I'm hoping this weekend to modify the proposal, 
making clear that the syntax presented is only for illustration of 
implications. Perhaps it can serve as one of many springboards for this 
discussion in the more formal standards process, which I'll trust to work out 
the concrete proposal.

Simon St.Laurent
Dynamic HTML: A Primer / XML: A Primer / Cookies


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