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Re: HTTP Protocol review

From: Chimezie Ogbuji <ogbujic@ccf.org>
Date: Tue, 18 May 2010 09:30:48 -0400
To: "Gregory Williams" <greg@evilfunhouse.com>
cc: "SPARQL Working Group" <public-rdf-dawg@w3.org>
Message-ID: <C8180EC8.119F0%ogbujic@ccf.org>
Greg,

On 5/17/10 8:27 PM, "Gregory Williams" <greg@evilfunhouse.com>
> The equivalent Update syntax given for POST is:
> 
> CREATE GRAPH <graph_uri>
> INSERT DATA { GRAPH <graph_uri> { .. RDF payload .. } }
> 
> The use of CREATE GRAPH here suggests that the POST operation will fail if the
> graph already exists. Is that right? If it doesn't exist, it's meant to be
> created on-the-fly, making this equivalent to PUT for non-existent graphs?

I removed CREATE GRAPH <..>, I think that was incorrect.  The insert use
case assumes the graph exists, so no need to create it.  The 'container
append' POST scenario is more equivalent to the PUT scenario where the
server provides the graph IRI.
 
>> If the embedded IRI does not correspond to an existing graph then it either
>> identifies a 'container resource' or it doesn't.  If it doesn't, the origin
>> server should return a 404, otherwise the operation should proceed as
>> defined.  I've added text clarifying this.
> 
> What is a "container resource"? Did I miss the definition somewhere, or is it
> defined in another spec? Is it just a graph IRI that already exists in the
> graph store? It seems to only be used in section 5.3, but I'm not actually
> sure what it is.
> 
> The text says a container resource is "designated by the origin server". How?

So, in the end I've added an editor's note.  This usecase was initially
given by Leigh Dodds in his initial comment and is a very common REST recipe
(the Atom Publishing Protocol has a notion of a Collection you can append in
this way).  The closest thing that would work is the network-manipulable RDF
dataset itself and the Service Description language provides for a way to
describe datasets, however, it is not clear (within the scope of this
protocol) what the user would dereference to get a description that gave
them the URI of the dataset that it can use to POST triples for a new graph.
Do you have some suggestions?

-- Chime


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Received on Tuesday, 18 May 2010 13:32:36 GMT

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