words (RE: extensibility in XSchema?)

[Rick Jelliffe]

> From: james anderson

> i thought you could do this with unparsed 
> (that is, external) entities only.
> (i don't understand why, but that's what 
> i thought the rec says) ?
> and, what's the difference between the cited example and the 
> following (modulo validation constraints)?
> 
> <!ATTLIST object   PI CDATA #IMPLIED >
> <object  PI="&x">A wooden horsey</object>

Oops, I made a big mistake here--whatever I was thinking of
it wasnt XML. Apologies and embarrassment. At the risk of putting
more feet in my mouth, here are two other methods for your
dissection.

Yes, XML only has external entities for ENTITY attributes,
and these are not parsed, except by some additional contraint.
(I think I was distracted by SGML, which can label entities as PIs,
rather in the fashion of professional wrestler George "the Animal"
Steele, who would be distracted by the turnbuckle and try to eat
it at critical moments in a match.)

So here is a better attempt:
 <!ENTITY xxx "xxx.jar#xxx">
 <!ATTLIST object   PI ENTITY #IMPLIED >
...
 <object PI="xxx">a wooden horse</object>

In this case the external, unparsed entity would be a code
fragment. So "object" has an attribute which names 
an entity which is declared as being the resource which
is a fragment of that java archive. (I wouldn't have to use
fragment identifiers, I could have one PI per external file.)
The MIME headers returning the resource give the equivalent 
information to the PI target (notation).  So there is still
a way to associate external processing instructions to XML
elements. 

I suppose an alternative leaves using an XLink href attribute to
point to a PI given previously in the document (if XPtr ends
up being able to locate PIs), though. But that is not XML.

Rick.




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