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Re: Update comment

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Wed, 23 Mar 2011 22:14:15 +0000
Message-ID: <4D8A70B7.2000305@epimorphics.com>
To: Lee Feigenbaum <lee@thefigtrees.net>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>


On 23/03/11 21:53, Lee Feigenbaum wrote:
> The SPARQL query spec only specifies an indirect relationship between
> graph name and contents for FROM and FROM NAMED, right?. USING should
> be the same thing -- I don't think I understand the problem?
>
> Lee

It's not the indirect relationship involved FROM NAMED (query sec 
13.2.2).  Let's just talk about FROM.

The problem is that FROM typically cause a graph to be read form the web 
(yes - not in Anzo or Mulgara, but that's unusual).

The update spec says USING is identical to FROM (it uses the word 
"identical").

So a reasonable expectation of an engine that reads from the web is that 
USING does as well. We added USING so the graph can be picked from the 
graph store so its not identical in such a system.

And the text goes onto indirectly imply this as well by talking about 
WITH which does mean a graph in the store.

Earlier:
"The WITH uri defines the graph"...
would be better as
"The WITH uri defines the graph in the graph store "...

	Andy


>
>
> On 3/23/11, Andy Seaborne<andy.seaborne@epimorphics.com>  wrote:
>> A Fuseki user found the text below and assumed
>>
>> INSERT
>>     {<http://rdf.freebase.com/ns/en.miles_davis>  ?p ?o }
>>     USING<http://rdf.freebase.com/ns/en.miles_davis>
>>     WHERE
>>     {<http://rdf.freebase.com/ns/en.miles_davis>  ?p ?o }
>>
>> was like
>>
>>
>>     CONSTRUCT
>>     {<http://rdf.freebase.com/ns/en.miles_davis>  ?p ?o }
>>     FROM<http://rdf.freebase.com/ns/en.miles_davis>
>>     WHERE
>>     {<http://rdf.freebase.com/ns/en.miles_davis>  ?p ?o }
>>
>> which it isn't (I hope).
>>
>>
>> 3.1.3 DELETE/INSERT
>> """
>> The USING<uri>  and USING NAMED<uri>  clauses affect the graphs and
>> named graphs used in the WHERE clause. This is identical manner to how
>> FROM<uri>  and FROM NAMED<uri>  clauses affect the graphs and named
>> graphs in a SPARQL SELECT query.
>> """
>>
>> In most systems (not all) FROM reads a graph from the web and makes it
>> part of the default graph.  It's LOAD.
>>
>> (Yes, *a few* systems pick their FROM out of the dataset)
>>
>> Doesn't USING select one or more graphs out of the graph store and use
>> that for default graph.  Reading from the web is not allowed (I hope).
>>
>> """
>> The use of USING in this instance is to avoid possible ambiguity of
>> where statements being DELETEd from. If a USING clause appears, then
>> this will override any effect that WITH may have on the WHERE clause,
>> and only the WHERE clause.
>> """
>>
>> What's "this instance"?
>>
>> 	Andy
>>
>>
Received on Wednesday, 23 March 2011 22:14:54 GMT

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