We would have to agree that containment equals 'has-a'.
What the XML containment semantic implies is up to the application
designer. That is so. One might argue that a zero occurrence
indicator says "might have-a".
But HAS-A can be agreed upon with no extra information being
added to the XML to indicate the agreement. IS-A can't. Or....
The point is that RDF semantics are RDF semantics. I don't see
a way out of the application IS-A application tautology. One
shouldn't compare XML semantics to RDF semantics. One should
understand what RDF semantics model and decide if that is
necessary for the application at hand or if a generalized
RDF processor (whatever it does) is doing something useful
for the system at hand.
len
From: Robin Cover [mailto:]
I'm not sure I agree with Len, if the claim is (?) that
XML explicitly models HAS-A.
For <foo><bar></bar></foo> we can say of the encoded
instance that "the element foo hierarchically contains the element
bar," but we have no authorization to believe that the
explicit structural relationship implies HAS-A. Maybe
bar HAS-A foo, maybe foo HAS-A bar, or maybe neither is
true if we understand HAS-A as representing the notion of
a property/attribute.
For <parent><child></child></parent> one could mean at the
application level that a parent has a child, or that a
child has a parent, or neither, or any of a thousand other
possible relationships that might be imagined; this structural
form "A hierarchically nested in B" licenses no interpretation
in terms of HAS-A, IS-A, IS-PART-OF, or anything else. Structurally
XML implies notions of is-adjacent-to, precedes, follows,
is-hierarchically-within [etc.] but a far as I know, these
structural relationships predicated of the serial encoding
have no authorized semantics in any domain.
Or... ?
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