[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

RE: Data Model(s) for XML 1.0 / XML Devcon / DOM / XSL / Query

• From: "Bullard, Claude L (Len)" <clbullar@i...>
• To: "W. E. Perry" <wperry@f...>, XML DEV <xml-dev@l...>
• Date: Fri, 23 Feb 2001 15:22:19 -0600

I think you get this, Walter, but let me make sure I do.
Loosely:

The problem is, the instance (XML UTF/ASCII file) 
does NOT contain the same information as the 
real "instance" (struct, object, table) pick one)). 
The data  actually being processed once the 
document is past the well-formed parse is subject 
to alteration.  For example, namespace processing 
adds information.  DTD processing adds information. 
Other processes such as XSLT transforms, XPath 
slicing and dicing, XQuery LETs, etc. operate not 
against XML, but against that post-parser data 
structure. (This isn't new:  SGML DTD processing 
added information too, (#FIXED) and we blithely 
said "the software handles this" and by gum, 
some did, some didn't, who knew. It was truly 
messy to buy an SGML system as a result.)

TODAY: per XML 1.0, we don't have a common model 
for what is in there.  In other words, a node 
IS-Not A Node per the properties the node has.  
In the grove world, they would say the original 
grove was not completely specified, so the grove 
plans for each process are noisy or simply, invalid.  
The Grove guys were right;  just hard to grok.

That makes it pretty hard to do something like 
XML Query because there is no way to ensure two 
implementations have the same data if they come 
from two different upstream processors.   The ONLY 
thing one can count on is the XML UTF file and 
that is just BagOCharacters. 

To do more than move bags, we need a common 
data model.  So far so good.  Question:  given 
the rate of specs coming out, how many MORE 
PVSI processes will be spec'd and will they 
force us to loop back again?  Before the 
XML community really takes Henry to heart here, 
let's ask that question and see if we think 
we have a reasonable answer.  Minimal victory 
solutions are MORE costly if the next step 
is a loopback. 

Len 
http://www.mp3.com/LenBullard

Ekam sat.h, Vipraah bahudhaa vadanti.
Daamyata. Datta. Dayadhvam.h


-----Original Message-----
From: W. E. Perry [mailto:wperry@f...]
Sent: Friday, February 23, 2001 2:40 PM
To: XML DEV
Subject: Re: Data Model(s) for XML 1.0 / XML Devcon / DOM / XSL / Query


Robin Cover wrote:

> Hmmm... You wrote:
>
> > By permitting an instance document to stand on
> > its own as syntax, without the expected pre-ordained
> > semantics expressed in a DTD.. XML took the decisive
> > step which SGML never had
>
> I don't understand, unless something is lurking in "expected" and/or in
> "pre-ordained".

What is lurking is the 'pre' in "pre-ordained" (which implies 'expected').
If
nothing is expected, then it is legitimate to consider only the body of the
instance document. If a content model or schema is desirable as a means to
describe the document structurally, generically, or abstractly, then it can
be
derived from the instance. 

• Prev by Date: Type Derivation by Restriction
• Next by Date: Re: Data Model(s) for XML 1.0 / XML Devcon / DOM / XSL / Query
• Previous by thread: RE: Data Model(s) for XML 1.0 / XML Devcon / DOM / XSL / Query
• Next by thread: Re: Data Model(s) for XML 1.0 / XML Devcon / DOM / XSL / Query
• Index(es):
  • Date
  • Thread