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RE: Summary of the QName to URI Mapping Problem

From: pat hayes <phayes@ai.uwf.edu>
Date: Fri, 31 Aug 2001 12:16:02 -0700
Message-Id: <v04210105b7b59137034a@[130.107.66.237]>
To: Patrick.Stickler@nokia.com
Cc: www-rdf-logic@w3.org
> > >But is this really an interaction of the semantics of the RDF graph
> > >and the semantics of the URI? I.e., aren't such mechanisms
> > really just
> > >instructions to the parser?
> >
> > You can look at it that way, indeed, and that might be the easiest
> > way for just this. I guess my point is really only a kind of gut
> > feeling/worry that we are going to have to be sensitive to ways in
> > which the classical syntax/semantic layerings are going to get more
> > complicated. Here's another example, from the RDF M&S (which has all
> > kinds of wierd stuff in it, by the way, that seems to be very little
> > used): section 3.4, aboutEachPrefix, which takes a URI prefix and
> > asserts something about all the things that are on the web that can
> > be retrieved by adding some extension to it. We didnt even try to
> > give this a formal meaning in the RDF model theory, but in order to
> > do so one would need to 'cross layers' rather drastically (not to
> > describe the result of 'expanding' aboutEachPrefix, thought of as a
> > preprocessing step - the current workaround - but to treat it as a
> > genuine language element and give it a coherent formal semantics.)
>
>But could not one consider that aboutEachPrefix is by nature somehow
>contrary to the opaque quality of URIs in the graph and therefore not
>part of the graph layer, but rather a form of processing instruction
>to be applied to graphs, like a specialized query?

Yeh, you could - we do. That's what I meant by a preprocessing step.

> Similar to the
>DAML 'include' instructions for fetching in other schemas. Thus, it
>needs no formal meaning in the RDF model theory.

Right. We can go on having these as exceptions and treating them 
exceptionally, but I feel that at some point we ought to take a 
harder look at them and try to see if they might not have something 
in common that would be worth treating more systematically; and that 
when we do, we will have to 'cross levels' and have a language which 
uses part of its syntax to talk about other parts of its syntax, and 
a semantics which applies to the whole thing at once.

> > Well, yes, in the RDF graph of a piece of DAML. But to be fair, DAML
> > itself doesnt claim to be a graph-based language.
>
>Fair enough, though I was mostly thinking of the actual RDF graph,
>i.e. that which would be distilled into triples. I.e., even though
>'include' instructions constitute extra information for a DAML parser,
>is that information also included in the RDF graph representation
>itself?

Actually I think it is, though it doesn't really make any semantic 
sense within RDF . But these languages are often used rather sloppily 
from a strictly semantic perspective, perhaps inevitably.

>From what I understand, it is not, so such instructions are
>not part of the "semantics" of the RDF graph itself, right?

They would not be if they weren't in the graph, right.

Pat Hayes

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Received on Friday, 31 August 2001 15:14:53 GMT

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