Comments, parsers, XPointers

[Paul Prescod]

Michael Kay wrote:
> 
> XPointer (and to some extent the DOM as well) in my view
> fails to recognise that XML defines two object models, a
> logical model and a physical model. SAX quite clearly and
> explicitly gives you access to the logical model only,
> whereas XPointer and DOM are rather ambiguous about the
> distinction.

XML has no semantics and thus no object models. :)

I am only half kidding. People are confused because the XML
REC is confused. Where does it say that CDATA sections and comments are
part of the physical and not logical structure? I agree that they 
*should be*, but where does it say that? Until XML's semantics are 
defined precisely, we must guess at them.

John E. Simpson wrote:
> 
> Well, as I just mentioned in a reply to DavidM, it's certainly not
> *critical* that comments be made available to downstream apps other than
> editors. But they seem to serve some valid purposes as well -- not
> necessarily just of the "remind the author what this next thing does."

I think that the semantics of comments should be precisely "remind the
author what this next thing means." No more and no less. Any use for
machine processing is abuse because it is bound to cause the problems you
are complaining about. Some parsers will strip them out (as is their
right). If you depend on that comment for anything more than source file
maintenance, then you are in trouble.

Paul Prescod  - http://itrc.uwaterloo.ca/~papresco

"A writer is also a citizen, a political animal, whether he likes it or 
not. But I do not accept that a writer has a greater obligation 
to society than a musician or a mason or a teacher. Everyone has
a citizen's commitment."  - Wole Soyinka, Africa's first Nobel Laureate


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