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Re: comments on SPARQL Query Language for RDF

From: Bob MacGregor <bmacgregor@siderean.com>
Date: Wed, 30 May 2007 00:00:24 -0700
Message-Id: <12D8052A-08E3-4FBD-9608-EE1EBE8F2889@siderean.com>
Cc: public-rdf-dawg-comments@w3.org, "Eric Prud'hommeaux" <eric@w3.org>, "Richard Newman" <rnewman@franz.com>
To: Pat Hayes <phayes@ihmc.us>
Hi Pat,

On May 29, 2007, at 1954, Pat Hayes wrote:

> <snip>

> However, I am at a loss to understand how you refer to these  
> 150,000 graphs if you have no way to name them. How do you even  
> know how many you have?

Each of the graphs consists of triples extracted from a different  
document.  The document might be identified by a file name, or a  
message ID,
a documentum identifier, or whatever.  The quads for that document  
share a common context argument; a blank node.  The same
blank node appears in subject position to record provenance  
assertions about the graph (which document, which extractor used,
time of extraction, etc).

> (It sounds from your description that you are in effect treating  
> the provenance as *being* the name of the graph. Does that  
> perspective help reconcile things?

You still seem to feel a need to name each graph.  Rows in a  
relational table don't have names and are still identifiable.  The  
same goes for graphs;
names are unnecessary, and not particularly useful.
>>
> There has to be some way for the query to refer to them. If you can  
> think of way of doing this without somehow naming them, please  
> explain it.
Hopefully, I just have.
>
> <snip>
> OK. Do you always query against the same set of unnamed graphs?

Yes in the short term.  New graphs are introduced on a continuing basis.

> If so, you can treat this as a single graph for purposes of  
> defining a SPARQL query answer.

Its a single graph if we ignore provenance, but not if we take  
provenance into account when we query.

Cheers, Bob
Received on Wednesday, 30 May 2007 07:00:34 GMT

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