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   Re: [xml-dev] heritage (was Re: [xml-dev] SGML on the Web)

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Hi Patrick,

>>The document that you quote is not a normative definition of XML.
>>There are many normative definitions of data models for XML,
>>including the Infoset and XPath.
> And it is luck that they all follow a tree based model?

Not luck. Firstly, XML syntax is structured to support a tree-based
model, because one of its well-formedness rules is that elements must
be nested inside each other. Secondly, a tree-based model is an
excellent choice for implementations since it makes it easy to keep
track of context and to focus processing onto particular subtrees;
these are advantages that are missed by APIs that don't assume a
tree-based model, such as SAX.

> Probably time to end this particular thread. I was trying to
> convince you that if everything the W3C has done with XML looks like
> a tree, then it must have a tree model.

How about that I agree that XML syntax is designed around a tree
model, and you agree that a tree model isn't the *only* way to
interpret a document in XML syntax? After all, as you've shown with
JITTs, the only thing that gives meaning/structure to a document is
the processor that's used on it.

> I have failed in that attempt and don't really have any other
> evidence to offer. (I don't consider a plethora of tree based data
> models persuasive at all that XML has a one syntax and many data
> models.)

That's a fair point, but what about SAX? Or the productions used to
describe XML syntax in the Recommendation? Neither of those are tree
models (or at least, the BNF parse tree doesn't follow the same kind
of tree as the one that you get in the DOM/XPath tree models).

> This is particularly important in light of your insistance that new
> models of XML must still comply with the well-formedness strictures
> of XML 1.0. You can have any model you like with XML, so long as it
> is tree based. (Or convert to some other model but I don't share
> your confidence in that strategy.)

Hmm... I'm not sure how to move forward on this one. I don't think
that anything will persuade me that a document that isn't well-formed
is in XML syntax. We'll just have to agree to disagree.



Jeni Tennison


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