Re: A bit of pedantry (was Personal reply to Edd Dumbill's XMLHackArticle. . .)

[Eric van der Vlist <vdv@dyomedea.com>]

"W. E. Perry" wrote:
> 
> Yes, there are layers. One underlying question in this discussion is which of
> those layers are inherently XML. In my experience of this list, and the community
> it serves, the extent of general agreement extends only so far as to include
> well-formed XML markup. Even within the XML 1.0 specification, the question of the
> canonical semantics of XML is raised by the optional nature of validation. The
> dividing line seems always to be a process. To elaborate from the syntax of an
> instance of well-formed XML the additional semantics of validity requires further
> processing. 

This is the key point.

To some of us (count me in), a layered architecture is a must, but I
wonder how far this belief is shared and there is always the question of
defining the layers.

I would say that we have already at least 5 (optional) layers (more if
you add XLink and XInclude): well formed XML before entity substitution,
well formed XML after entity substitution, validated XML, namespaced XML
and typed XML.

Acknowledging these layers would allow to define an infoset per layer
and to propose layered SAX [1] and DOM interfaces, each layer adding
information to what it gets from the previous one.

Representing all these layers as XML would give a consistent view and
access.

Eric

[1] http://lists.xml.org/archives/xml-dev/200012/msg00043.html
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Eric van der Vlist       Dyomedea                    http://dyomedea.com
http://xmlfr.org         http://4xt.org              http://ducotede.com
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