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Re: Name of a graph? and FROM and FROM NAMED

From: Dan Connolly <connolly@w3.org>
Date: Thu, 02 Jun 2005 08:37:42 -0500
To: Yoshio FUKUSHIGE <fuku@w3.org>
Cc: public-rdf-dawg@w3.org
Message-Id: <1117719462.19175.195.camel@localhost>

On Thu, 2005-06-02 at 19:12 +0900, Yoshio FUKUSHIGE wrote:
[...]
> aggregator.
> 8.4
> [[
>  Each time a graph is read into the aggregator, it is given a URI by the 
> local system.
> ]]
> but, so it may not be the same URI the graph had BEFORE being aggregated,
> which means we cannot know the name of a named graph without asking (but 
> how?) !

This reminds me of something I have been meaning to comment on...
perhaps not exactly the same issue, but nearby...

If I write

  SELECT ?who FROM NAMED <alice> <bob> WHERE
    GRAPH <alice> { <alice#me> foaf:knows ?who }
    GRAPH <bob> { <bob#me> foaf:knows ?who }

then we've got two (or more) "named graphs" in the dataset.
This suggests that (the absolute form of) <alice> is
a/the name of a graph. This is somewhat misleading, w.r.t.
web architecture, which says that <alice> identifies
a resource that has a representation that is a graph.
The query might be run twice and get two different answers
because the state of the <alice> resource changed; i.e.
it was represented by a different graph. So to say that
<alice> is the name of a graph is a little goofy.

cwm uses a log:semantics property to make the indirection
explicit. I don't suggest we go there in SPARQL, but
in http://lists.w3.org/Archives/Public/semantic-web/2005Jun/0004
I see

> E.g. using TriG, the dataset from Example 1 in section 7.1 of
> the SPARQL spec could be unambiguously serialized as:
...
> :bg
> {
>    <http://example.org/bob>    dc:publisher  "Bob" .
>    <http://example.org/alice>  dc:publisher  "Alice" .
> }

and the TriG spec (http://www.wiwiss.fu-berlin.de/suhl/bizer/TriG/ )
says that's short for

  :bg :- { ... }
which pretty much means
  :bg owl:sameAs { ... }

but the in a SPARQL dataset, the relationship is more like

  :bq log:semantics { ... }


I haven't thought of any actual replacement for
the "named" terminology, so I'll suggest a note ala:

   NOTE: The "FROM NAMED" syntax suggests that the URI
   identifies the corresponding graph, but actually the
   relationship between a URI and a graph in an RDF dataset
   is indirect: the URI identifies a resource, and the
   resource is represented by a graph (or, more precisely:
   by a document that serializes a graph). See also
   the diagram in section "1. Introduction" of
   [webarch].


Hmm... bummer that diagram doesn't have a number/label.
http://www.w3.org/TR/webarch/#intro


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Thursday, 2 June 2005 13:37:51 GMT

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