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Re: Dataypes, literals, syntax

From: Geoff Chappell <geoff@sover.net>
Date: Sat, 3 Aug 2002 09:56:13 -0400
Message-ID: <09e701c23af5$8937a8c0$825ec6d1@goat1>
To: "Sampo Syreeni" <decoy@iki.fi>
Cc: <www-rdf-logic@w3.org>


----- Original Message -----
From: "Sampo Syreeni" <decoy@iki.fi>
To: "Geoff Chappell" <geoff@sover.net>
Cc: <www-rdf-logic@w3.org>
Sent: Friday, August 02, 2002 8:02 AM
Subject: Re: Dataypes, literals, syntax


>
> On 2002-08-01, Geoff Chappell uttered to Sampo Syreeni:
>
> >If we're talking about (as opposed to with) literals, I guess we're
> >taking the position that literals are tidy? i.e. that they denote
> >themselves?
>
> Emm... As far as syntax goes, I'm in the tidy camp. However, I do not
> agree with the interpretation of tidy as "denoting itself". I view
> tidiness purely as a syntactic construct, that is, one consequence of
> constraining the model to a set of triples.
>
> >> o1==("aho","fi",false)
> >> o2==("aho","ja",false) .
> >
> >As names, these two things (rdf literals) are clearly different. But
_taking
> >the untidy position_, absent other information, how do I know that these
two
> >names don't refer to the same object?
>
> You don't. Again, I would take this from the point of view of the layer
> cake. At this level we're dealing with syntax, so if the kind of extension
> I propose were to be made, the current two parse types would have to be
> taken as datatypes with datatype mappings taking strings with certain
> languages to themselves. They would make the literals tidy (as in "denote
> themselves"), whereas other datatypes perhaps wouldn't. However, at a
> higher level you might well treat certain syntactically unequal things as
> equal. "ad hoc" as a Latin and English string is two different things as
> far as syntax (the base RDF data model) goes, but had you something above
> in the cake which actually understood the semantics (one such thing being
> XSD), it might well want to treat these as equal. The point is that both
> have to be expressible separately in case the upper layers take a
> different viewpoint, and decide to treat them as inequal.

But doesn't that just treat the lower layers like syntax for the upper
layer? is that really the type of layering that we want? I'd think that the
layers should at least be sharing the same domain (i.e. be talking about the
same things) to be able to claim interoperability between the layers. I can
see that a higher layer might add additional meaning to some statements to
further constrain interpretations and might deny the usual meaning of others
(e.g. to hide the syntactic machinery of the higher level within the lower
level as with the dark triple approach), but should it be possible for a two
layers to come up with a different interpretation of the same node? I can
see that a higher level could easily infer additional nodes by dereferencing
the name(s) of the lower level (i.e. by explicitly changing the denotation
level) but doesn't that likely lead to similar problems as appear in the rdf
datatype debate - e.g. a property ending up with a range that includes the
lexical and value spaces of a datatype?

--geoff
Received on Saturday, 3 August 2002 09:26:50 UTC

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