Musing over Namespaces

[Arjun Ray]

On Mon, 20 Dec 1999, Rick Jelliffe wrote:
>  From: Arjun Ray <aray at q2.net>
> >On Sat, 18 Dec 1999, Len Bullard wrote:
> >> Dan Brickley wrote:

> >How about improving DTDs? (Just a thought.)
> 
> ISO has a correction to SGML in the wings to allow alternative
> schema syntaxes to DTDs: I think it has been waiting for 2 years.

Is there anything on this at the WG4 site?  (And/Or is this another
implication of SEEALSO?)

> I think the problem with extending DTDs is that you have to create
> new declarations (unless you use PIs): 

That was the thought:)  HyTime jumped through a gazillion hoops and still
wound up using "new" declaration-style syntax in the LTDR (not to mention
the pre-WebSGML stuff in the AFDRmeta notation.)  

> also, DTDs are much more aimed at parsing while what is needed is at a
> different level: structures, datatypes, semantics.

Structures, yes; datatypes, maybe (I'm not convinced that regexes aren't
enough for a syntactic formalism); semantics, no.  A machine processable
meta description (itself a "semantic"!) for any imaginable semantic system
or requirement sounds like pinning a tail on the DWIM.  Here I think SGML
got the theory exactly right: there is a point at which one really
shouldn't try to do better than declare a notation.  We need more and
better ways to refer to notations, as well as new declarative types to
take the pressure off having to tuck something away in an opaque notation
declaration just because ISO8879 doesn't provide (syntactic) machinery.

An extensible syntax for declarations...:)

> There is also the issue that different classes of languages have
> different families of constraints.  

And "one syntax fits all" can be limiting...?

[ re testing utility of the new schema drafts:]
> For example, are you happy that XML Schemas make infoset
> contributions?

No.  The Infoset is the Universe of Discourse ("all the names to name the
names"), and schemas should be layered on top.  Schemas contributing to
infosets is like moving the goalposts.

> Should there be mechanisms in place by which a document can say "I use
> infoset contributions: if you don't have a full XML processor, don't
> accept me!"

Doesn't this come down to notation declarations?  ("I use *these*
thingummies: bail out if you don't grok")

> Or, what should the criteria for validity be: structures, structures +
> datatypes, structure+ datatypes + encoding-checking?

Schemas should provide for all three; the receiver decides what it needs.

> Or should it implement an ANY like XML DTDs (any element that is
> defined) or like WF XML (accept anything)?

"Archetype" seems to have been lost in the shuffle.  IMHO, that was the
way to go.

> The new drafts are said to be "feature complete", so this is a good time
> to start reading and thinking "could I actually use this thing?"

Yep.


Arjun


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