Dear Tim,
Le 01/07/2010 20:03, Tim Finin a écrit :
On 7/1/10 2:51 PM, Henry Story wrote:
> ...
So just as a matter of interest, imagine a new syntax came along that
allowed literals in
subject position, could you not write a serialiser for it that turned
"123" length 3 .
Into
_:b owl:sameAs "123";
length 3.
?
So that really you'd have to do no work at all?
Just wondering....
Isn't owl:sameAs defined to be a relation between two
URI references?
Not exactly. OWL DL defines this restriction on owl:sameAs, but
owl:sameAs is not itself defined like this. Plus, OWL DL is
syntactically a restriction of OWL (Full) (that is, a syntactic
restriction of RDF). The current discussion is about RDF, so I don't see
any reason to mention the specificities of OWL DL here. OWL DL, in any
case, would forbid literals in subject position.
Even if not, it is symmetric and
would have the above imply {"123" owl:sameAs _:b .}
No it does not imply this because "this" is not in the language. The
language RDF tells you that triples (the formulas in that language) have
no literals as subjects. In any logical formalism, you cannot infer
things that are not in the language.
This is actually what is strange about not allowing literals in the
subject position: you cannot say things like:
"123" owl:sameAs "123"
and therefore, you cannot infer it. If, for any reason, you want to
infer this, it means that you are in need of a modification of the RDF
language which allows literal in the subject position.
Yet, to make things more confusing, the interpretation of the predicate
owl:sameAs, under the OWL semantics, is reflexive and symmetric.
I am preparing an email about the weird consequences of excluding
literals in subject position.
Regards,
--
Antoine Zimmermann
Post-doctoral researcher at:
Digital Enterprise Research Institute
National University of Ireland, Galway
IDA Business Park
Lower Dangan
Galway, Ireland
antoine.zimmerm...@deri.org
http://vmgal34.deri.ie/~antzim/
