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   Re: [xml-dev] Stupid Question (was RE: [xml-dev] XML doesn't deserve its

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Mike Champion wrote:
> 3/5/2002 5:55:15 PM, Joe English <jenglish@flightlab.com> wrote:
> >I'm having a hard time envisioning a scenario where having
> >'xsi:type' would be useful to an application.
> Well, I have that same problem with the PSVI :~)  Seriously,
> would this apply to having the PSVI tell you the type of
> the element as well as having xsi:type tell you the type
> of the element?

More or less, yes.

The general idea of Infoset augmentation is I think very useful,
but I'm starting to think that doing it as part of validation
is not a good idea.  Schema languages for validation should
be as powerful (and expensive) as needed to express a wide
range of constraints, but schema languages for augmentation
should be as simple (and cheap) as possible.

RELAX-NG and Schematron are at the right level of complexity
for validation languages; they're very expressive, but they don't
add anything to the infoset other than "OK/not OK" (and in the
case of Schematron, a detailed explanation of why it's not OK).

EXPLICIT LINK is pretty close to the right level of simplicity
for an augmenting language.  Were it not for two or three
fatal flaws in the specification it would be ideal.

W3C XML Schema tries to do both at the same time, and both sides
suffer.  Besides that, only a few of the W3C XML Schema PSVI
contributions look very useful to me  -- "schema default", and
maybe the ID/IDRef properties.

Getting back to (what I think was :-) the original point,
I agree (I think) that adding attributes is a better way
to augment an infoset than adding "information items" with
an unspecified implementation.  That way everything fits
into the basic "elements, attributes, and text" framework.

--Joe English



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