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Re: SOURCE : handling a graph read in twice at different times

From: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
Date: Mon, 17 Jan 2005 10:25:56 +0000
To: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-ID: <20050117102556.GA22096@login.ecs.soton.ac.uk>

On Sun, Jan 16, 2005 at 04:42:59 +0000, Andy Seaborne wrote:
> >Great, but whats the purpose of the FROM and GRAPH keywords here? Are they
> >to illustrate something I'm missing, or are they neccesary?
> 
> Illustrating.  Quoting from earlier: "Use of FROM or GRAPH is optional"
> 
> My command line apps can't construct arbitrary RDF datasets from command 
> line arguments yet.  The manifest form can't describe them either.  They 
> can be specified in queries themselves.  Putting then in was just to make 
> the point and avoided writing a (small) custom program when the computer 
> could already do it.

OK, I'm missing something, I'l reread the relvent section and see if I can
find what I missed.
 
> >Also, if you read in a graph that has:
> >
> ><owl:Ontology rdf:about="">
> >  ...
> ></owl:Ontology>
> >
> >Does the ... get assertad with urn:x-local:foo, or the resolved URI as its
> >subject?
> 
> The URI where the graph was read from - the external one - the http:// in
> the above.  rdf:about="" is just shorthand and the relative URI resolution
> rules apply before local handling.

OK, 3store currently uses the internal one, but theres no good reason for
that.
 
> An alternative modelling would be to have internal URIs to represent the
> event of reading the remote graph:
> 
> <urn:x-local:graph1>
>     :read      "2005-01-16T03:8:03Z"  ;
>     :readFrom  <http://example.org/foaf/graph> ;
>     :size      23563 ;
>     :processingApplied  :rdfsRuleSet ;
>     :cause     <dailyUpdate> .
> 
> 
> (the test case is a slight cheat - it isn't clear what the dc:date
> refers to but it is an "event of interest", but you can't have another date 
> now without confusion).

Right, for this reason I assert an event instance, something link:

<urn:x-local:graph1>
	:last-updated _:3;
	:updated      _:3;
	:updated      _:2;
	:updated      _:1.
_:3 dc:date "2005-01-17T10:19:00Z" ;
...

But I dont see the need to standardise this housekeeping, at least not yet.
I dont feel that I've refined it enough myself.
 
> ---- Keywords:
> 
> The use of the word "SOURCE" is a bit weak.  GRAPH would have been clearer
> and in a clearing out of the grammar, maybe using GRAPH for SOURCE (as GRAPH
> is a valuable keyword).

I dont mind either way, but I think someone had a reason not to use GRAPH
for thats currently SOURCE at the bristol ftf.
 
> FROM is SQL heritage back from rdfdb has:
> """
>   select [variable1, variable2, ... ... ] from {database}
> """
> 
> So:
> 
> s/GRAPH/USE/
> s/SOURCE/GRAPH/
> 
> any suggestions for specifying the unnamed graph (currently FROM) and named
> graphs (currently GRAPH) would be very welcome.
> 
> I'd also like the FROM/USE (current FROM/GRAPH) to come before the SELECT.
> With PREFIX etc first, it seems more natural to me to have all setup first.

Agreed.

- Steve
Received on Monday, 17 January 2005 10:25:58 GMT

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