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Re: Proposed N-Triples changes for datatypes & (untidy) literals

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Mon, 23 Sep 2002 14:49:58 +0300
Message-ID: <009e01c262f7$57bd67b0$d74416ac@NOE.Nokia.com>
To: "ext Jeremy Carroll" <jjc@hplb.hpl.hp.com>, "Dave Beckett" <dave.beckett@bristol.ac.uk>, "RDF Core" <w3c-rdfcore-wg@w3.org>



[Patrick Stickler, Nokia/Finland, (+358 50) 483 9453, patrick.stickler@nokia.com]


----- Original Message -----
From: "ext Jeremy Carroll" <jjc@hplb.hpl.hp.com>
To: "Patrick Stickler" <patrick.stickler@nokia.com>; "ext Jeremy Carroll" <jjc@hplb.hpl.hp.com>; "Dave Beckett"
<dave.beckett@bristol.ac.uk>; "RDF Core" <w3c-rdfcore-wg@w3.org>
Sent: 23 September, 2002 14:20
Subject: RE: Proposed N-Triples changes for datatypes & (untidy) literals


>
> >
> > Only parsers need change, so that they give the inline literals
> > the needed systemID prefix.
>
> This fails the old self-entailment test:
>
> <rdf:Description>
>   <eg:name>Patrick Stickler</eg:name>
> </rdf:Description>
>
> is neither equal to, not does it entail,
>
> <rdf:Description>
>   <eg:name>Patrick Stickler</eg:name>
> </rdf:Description>
>
> A position that was rejected a long time back.

Hmmm... but was this old self-entailment test based on a presumption
of tidy semantics? It appears it was. And thus, it may now be
a broken or invalid test as it does not in fact reflect the
new semantics of inline literals.

If we are in fact going to presume that

1. Inline literals have untidy semantics
2. Entailments are based on semantics (right?)
3. The meaning of inline literals is unknown in the absence
   of explicit knowledge of the datatype by which the
   lexical form is to be interpreted

then it is not unreasonable that the above entailment cannot be
determined in the absence of an rdfs:range datatyping assertion for
the eg:name property, since string-equality of lexical forms
does not (necessarily) reflect value-equality.

And we cannot infer value-equality by the two triples having
both the same property and the same lexical form, since it has been
shown that general properties such as rdf:li or similar provide no
semantically distinct context as does a datatype (and in such
cases, local/explicit datatyping is the only mechanism to make
explicit the datatypes of literal objects of such general or
collection membership properties).

Thus, while it is the case that most properties which take
inline literal objects tend to be associated with a datatype
and thus appear to provide a semantically distinct context
for interpretation, one may not in fact base any tests of
equality on the property alone and thus entailments such
as above cannot be determined without the datatype.

I'm still not convinced, though, that the above could not be
made to entail itself in the MT, since the systemID of the
implicitly typed literal (the _:x in _:x"foo") acts
like a bnode nodeID of a datatype, and can be treated in
like manner.

I.e., if we are to parse the RDF/XML twice, each instance of
the <rdf:Description> element will result in a different bnode.
How can the first subject bnode entail the second, both of which
have string-unequal labels, yet the first implicitly datatyped
lexical form cannot entail the second? Seems like analogous cases
to me.

I would assert, though, that the following (if allowed) would
clearly reflect self entailment of untidy inline literals:

<rdf:Description>
  <eg:name rdf:nodeID="_:x">Patrick Stickler</eg:name>
</rdf:Description>

entails

<rdf:Description>
  <eg:name rdf:nodeID="_:x">Patrick Stickler</eg:name>
</rdf:Description>
Received on Monday, 23 September 2002 07:55:19 EDT

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