Hi Chris,
So I presume you have read the w3c page at:
http://www.w3.org/TR/rdf-sparql-query/#namedAndDefaultGraph
The following blog post provides some pointers on this:
http://www.snee.com/bobdc.blog/2009/03/querying-a-set-of-named-rdf-gr.html
The main value of the default graph to my knowledge is to ensure that if no
graph is specified using the "from" or "from named" clauses the specified
default graph will be used thereby preventing the query being run over all
graphs in the store which could have serious performance implications ...
Best Regards
Hugh Williams
Professional Services
OpenLink Software
Web: http://www.openlinksw.com
Support: http://support.openlinksw.com
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On 6 Jul 2010, at 13:16, Chris Wj wrote:
> Thank you for the help and the pointer. Could anyone provide some thoughts or
> pointers to places where I can learn the major differences between the two
> concepts (default vs named)? I've searched the w3c pages a bit and I am still
> unsure as to the value of the default graphs.
>
> On Mon, Jul 5, 2010 at 7:38 PM, Hugh Williams <[email protected]>
> wrote:
> Hi Chris,
>
> Details on how Virtuoso handles default and named graphs can be found in the
> online documentation at:
>
> http://docs.openlinksw.com/virtuoso/rdfsparql.html#rdfdefaultgraph
>
> Multiple default graphs can be specified with the "define
> input:default-graph-uri..." clause, and the "FROM NAMED..." clause can
> specified multiple times in a query ...
> Best Regards
> Hugh Williams
> Professional Services
> OpenLink Software
> Web: http://www.openlinksw.com
> Support: http://support.openlinksw.com
> Forums: http://boards.openlinksw.com/support
> Twitter: http://twitter.com/OpenLink
>
> On 5 Jul 2010, at 20:01, Chris Wj wrote:
>
> > How does Virtuoso handle default graphs? Can you specify multiple default
> > graphs? For example, 2 queries, 2 different default graph URIs. If so, is
> > there a way to query for the URIs of default graphs like you do with Named
> > Graphs?
> >
> > -Chris
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