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RE: Named graphs etc

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Mon, 23 Feb 2004 16:32:35 +0100
To: "Pat Hayes" <phayes@ihmc.us>, "Jeremy Carroll" <jjc@hplb.hpl.hp.com>, <Patrick.Stickler@nokia.com>, <chris@bizer.de>
Cc: <www-archive@w3.org>
Message-ID: <BHEGLCKMOHGLGNOKPGHDGELACCAA.jjc@hpl.hp.com>



I have been being beaten up further from the pragmatic wing  by Chris
Bizer - He is beginning to convince me ...


My understanding of his key arguments is as follows:

- use vocab as much as possible, not syntactic mechanisms
    : impacts graphset tag name
              asserted attribute

- meaning of vocab is shared: for example log:implies is ill-formed RDF,
because to make sense of it you have to use a second interpretation that
interprets concepts differently from the first. So the liar paradox is
resolved by saying that RDF is not a general purpose meta language for
logic.
   : impacts semantics, outlaws log: vocab

- the de re/de dicto argument is hence resolved largely in favour of de re,
but to some extent is seen as a red herring. For provenance information it
is certainly helpful to regard the provenance statements as being about a
'de dicto' graph; but this is not because we doubt that the author may be
using the URIs differently from us.
   : impacts semantics
  I guess one way of doing this is to say that the interpretation of the
name of a graph is the pair consisting of the graph and a set of the
interpreted triples, and the predicate selects which member of the pair is
interesting...


- whether we believe any graph or not is a matter for the trust layer.
Example below. Chris's PhD (in progress) is on the trust layer.  His
approach is very pragmatic - users have a trust policy that can take into
account facts about the contents and or use of a graph to determine whether
to believe it. Such a policy is not a logically mechanism, much more
prgamatic and down-to-earth. This makes the distinction between asserted and
non-asserted graphs redundant.

- the graphset in trix is merely a syntactic necessity for XML documents,
and should not convey any meaning. If we want to talk about a collection in
RDF there are plenty of mechanisms. So if we want to talk about a collection
of graphs we use one of those. Thus, the graphset tag should be changed to
something semantic-free (e.g. trix). It should be explicitly stated that the
URL used to retrieve a trix document refers to the document and not to the
contained graphs. The point here is to stop before going on the slippery
slop to graphsetsetsets


His words are at:
http://lists.w3.org/Archives/Public/www-archive/2004Feb/att-0050/namedGraphD
iscussion009.pdf


Example: Provenance Chains
Peter states, that Chris said that Andy said, that Monica Murphy is a
person.

G1 (Monica ex:hasName "Monica Murphy".
    Monica rdf:type ex:Person)

G2 (G1 ex:saidby Andy.
    G1 ex:DocumentURL Doc1.trix.
    G1 dc:date "2/10/2004")

G3 (G2 ex:saidby Chris.
    G2 ex:DocumentURL Doc2.trix.
    G2 dc:date "2/10/2004")

G4 (G1 dc:author Peter.
    G2 dc:author Peter.
    G3 dc:author Peter.)

G5 (G4 dc:author Peter.
    G4 dc:date "2/10/2004")

Depending on our trust policy we might believe some, all or none of the
above triples...


Jeremy
Received on Monday, 23 February 2004 10:33:29 GMT

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