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Update protocol and dataset description

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Fri, 05 Aug 2011 08:58:09 +0100
Message-ID: <4E3BA291.3080000@epimorphics.com>
To: SPARQL Working Group <public-rdf-dawg@w3.org>
The update protocol allows default-graph-uri and named-graph-uri in 
update requests.

I'm not sure this is a good idea:

In query, it's used to retarget or set the target dataset of a single 
query, overriding FROM/FROM NAMED.  Typical use is in web forms to set 
the target of the query for a general query processor, one that does not 
have any implicit dataset.

1/ Update is not the same - an update request is several operations, 
some of which might have USING/USING NAMED and others don't.

Use default-graph-uri and named-graph-uri for the update dataset 
collapses the USING/USING NAMED so changing the update request so that 
different operations no longer see different datasets.

It seemed to be to be better for USING/USING NAMED in update not to be 
overridden as it looses something of the update structure.

2/ Query is stateless - update is state changing.  Retargetting a query 
(maybe for testing) causes no state change.  Update is state change so 
retargetting needs to be done by setting up a different service.

3/ When I first read it, I more naturally tended to see it as defining 
the graph store.  In query it defined the target (RDF dataset) and in 
update it does not define the overall target.

4/ The Update Langauge doc does not have the facility to have a 
different dataset for the WHERE clause to the graph store. [1]


Could someone provide the use case for this feature and why it should 
override USING/USING NAMED?

	Andy




[1]
http://www.w3.org/2009/sparql/docs/update-1.1/Overview.xml#mappingRequestsToOperations
Received on Friday, 5 August 2011 07:58:42 GMT

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