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Denotation of datatype values

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Mon, 08 Apr 2002 12:38:43 +0300
To: RDF Core <w3c-rdfcore-wg@w3.org>
Message-ID: <B8D73FD3.12A8B%patrick.stickler@nokia.com>

Jeremy's recent posts regarding entailments between the idioms
suggests that there is an important question that seems to need
answering, namely, do we wish/expect/need that a given datatype
value (member of a datatype value space) always and only be
denoted by a single node in the graph? (as opposed to it being
denoted by a combination of nodes or statements such as the
inline idiom with an rdfd:range assertion).

If the answer to that question is no, then I don't see any
problem with the present proposal. The lexical form and
datatype property idioms provide single node denotation. The
inline idiom does not. But that is just the way things are.
(see below)

It seems that Jeremy's answer would be yes, which is why the
present proposal (which does not provide a single node
denotation for the inline idiom) is unnacceptable.

If the answer to the question actually is yes, then I see
two reasonable options:

1. Exclude the inline idiom from the datatyping solution. If
folks use it, fine, but it will have no official interpretation
and its use will be application-specific. The bnode of the
lexical form or datatype property idioms denotes the value
and if you don't use one of those idioms, you don't have any
explicit denotation of the value in the graph and you're not
doing "standard" RDF Datatyping.

2. Make literals untidy and have the literal node denote the
value in the case of the inline idiom. Though, this introduces
an oddness to the bnode idioms if the bnode then denotes the
value and the literal node object of rdfd:lex or
datatype property does not (i.e. is just the literal) unless
we say that for the bnode idioms both the bnode and the literal
node denote the value (which is still odd).


My personal feeling is that the answer need not be yes, in
that it need not be an absolute requirement that the value
always and only have a single node denotation.

We may simply accept that the inline idiom does not provide an
explicit, single node denotation of the value and if you
need/want such an explicit, single node denotation, don't use
the inline idiom -- or transform all occurrences of the inline
idiom to the lexical form idiom (or some other idiom) for your
specific application.

But this is a question for the WG to decide, and that decision
should be made as soon as possible. It may very well be that
OWL, DAML, etc. require only single node denotation and allowing
even the possibility of the inline idiom is problemmatic, in
which case, we should give such needs serious consideration in
deciding an answer to this question.

I expect that this decsision can be made via email discussion,
but we could also include it in this Friday's aggenda (Brian?).


Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Monday, 8 April 2002 05:36:12 UTC

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