Hi Ivan,
Thanks for your comments here. This is the first time the @role ==
rdf:type issue has been discussed at the level of RDF, and I've felt
very uneasy that it hasn't been gone through in detail before being
dismissed.
On 05/07/07, Ivan Herman <[EMAIL PROTECTED]> wrote:
Well... if you two guys still disagree after all these years, that may
be one more argument _against_ using @role (not necessarily _for_
@class, another attribute might also do...):-)
:)
> In RDF, if you say something is of type 'x' then all sorts of other
> statements become legitimate. So if I firstly say that 'a toolbar' has
> a property of 'collection of buttons', and then I subsequently say
> that 'the second <div> in my document is a toolbar', then it is
> legitimate to act as if the second <div> in my document has a property
> of 'collection of buttons'.
>
Mark, for the records, I am not sure this is true. To formalize it in
RDF what you seem to say is that if:
[[[
toolbar a rdfs:Class.
collectionOfButtons a rdfs:Property;
rdfs:domain toolbar.
2ndDiv a toolbar.
]]]
then we can deduce that... what? Only that
2ndDiv collectionOfButtons "something".
is consistent with these, but we _cannot_ deduce that such a triple
exists somewhere.
Right. But I'm not saying such a triple exists, only that it would be
legitimate to create such a triple--i.e., to use inference.
You can do what you describe with OWL cardinality constraints describing
things on collectionOfButtons...
Actually, we can do something different with those. If the facts are that
[[[
toolbar a rdfs:Class.
collectionOfButtons a rdfs:Property;
rdfs:domain toolbar.
2ndDiv collectionOfButtons "something".
]]]
then even in RDFS we can deduce that
[[[
2ndDiv a toolbar.
]]]
which is somewhat different from what you said.
That's also true, but where did you get the collectionOfButtons
property from for 2ndDiv? It's not in the original mark-up, and it
could only get created (in the sense of being infered) if we were to
say that @role == rdf:type. So we wouldn't be _deducing_:
2ndDiv a toolbar .
since we already know said it was, because of @role. (Hypothetically.)
The second example shows that, indeed, rdf typing may have consequences
(for example if OWL is used), ie, your core argument holds, just the
example does not:-)
:) I think my example is ok, but I don't really mind. As you say, from
many directions we can see that setting @role to mean rdf:type could
cause problems. My secondary argument is that doing this doesn't
actually gain us anything, and some system is still free to infer from
this:
2ndDiv role toolbar.
the rdf:type equivalent if it wants to:
2ndDiv a toolbar.
Regards,
Mark
--
Mark Birbeck, formsPlayer
[EMAIL PROTECTED] | +44 (0) 20 7689 9232
http://www.formsPlayer.com | http://internet-apps.blogspot.com
standards. innovation.
