W3C home > Mailing lists > Public > public-rdf-wg@w3.org > February 2012

Re: Three solution designs to the first three Graphs use cases

From: Lee Feigenbaum <lee@thefigtrees.net>
Date: Wed, 01 Feb 2012 10:55:31 -0500
Message-ID: <4F296073.3070008@thefigtrees.net>
To: David Wood <david@3roundstones.com>
CC: Alex Hall <alexhall@revelytix.com>, Andy Seaborne <andy.seaborne@epimorphics.com>, public-rdf-wg@w3.org
On 2/1/2012 10:35 AM, David Wood wrote:
> On Feb 1, 2012, at 10:30, Alex Hall wrote:
>
>> On Wed, Feb 1, 2012 at 8:58 AM, Andy Seaborne
>> <andy.seaborne@epimorphics.com <mailto:andy.seaborne@epimorphics.com>>
>> wrote:
>>
>>
>>
>>     On 01/02/12 13:40, David Wood wrote:
>>
>>                     >>> <s> <p> {<a> <b> <c> }
>>                     >>>
>>                     >>> you mint an identifier (<g1> ) then store
>>                     these quads:
>>                     >>>
>>                     >>> <s> <p> <g1> DEFAULT
>>                     >>> <a> <b> <c> <g1>
>>
>>                 >>
>>                 >>
>>                 >> For what it is worth, this is what Mulgara does.
>>
>>
>> Actually, this is incorrect. Mulgara will never mint a new graph
>> identifier for you. Mulgara doesn't even support any multi-graph
>> formats, since its developers have been busy with their day jobs :-)
>
>
> Alex is correct that Mulgara doesn't support graph literals, nor
> automatically generate new graphs. However, it does allow for the
> creation of new graphs (on command) and the storage of the graph
> relationships as the last element of the quads.

That's what most graph stores support, right? But it's still pretty 
different from what Sandro was suggesting?

Lee

> Regards,
> Dave
>
>
>>
>> Mulgara only supports single-graph formats (RDF/XML, Turtle, RDFa) and
>> you must explicitly tell Mulgara the URI of the graph into which you
>> are loading a document. There's no SPARQL 1.1 support (see "day jobs"
>> above) so you can't insert into the default graph.
>>
>>             >
>>             > David,
>>             >
>>             > Does Mulgara claim to support graph literals?
>>
>>         Mulgara supports what it calls named graphs. In fact,
>>         you*can't* query Mulgara (or its predecessors) without
>>         querying a particular graph. Our original query language (TQL)
>>         forced you to name a graph; the SPARQL implementation defaults
>>         to the default graph as configured, I believe. Each quad is
>>         indexed with its graph membership.
>>
>>
>>         There are some "special" graphs in Mulgara, especially the
>>         "system" graph that stores triples about all the graphs that
>>         the system holds. They are exposed and queryable.
>>
>>
>> Right, but named graphs and graph literals are very different. It's
>> true that one possible implementation of graph literals is to use
>> specially-minted internal graph ID's, but Mulgara doesn't do that.
>>
>>
>>             >
>>             > What does
>>             >
>>             > SELECT ?o {<s> <p> ?o }
>>             >
>>             > return?
>>
>>         If you queried the system graph thusly you would get the list
>>         of graph URIs held by that Mulgara instance.
>>
>>
>>     Query the configured default graph.
>>
>>     Does ?o return {<a> <b> <c> } or <g1> or something else?
>>
>>     (By the way - is the data syntax for graph literals understood by
>>     Mulgara documented anywhere?)
>>
>>
>> Just to be clear, Mulgara claims no support for graph literals.
>>
>> -Alex
>>
>
Received on Wednesday, 1 February 2012 15:55:54 UTC

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