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Re: [Bigdata-developers] equivalent of Jena TDB urn:x-arq:UnionGraph
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From: Bryan T. <br...@sy...> - 2015-09-14 11:06:34
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I am not sure what level you want to use here. Internally, we process a
default graph access path in a variety of different ways depending on the
cardinality of the named graphs in the default graph vs the set of all
named graphs. However, except for the cases where it reduces to either a
single graph or no graphs, we always wind up imposing a filter on the
iterator to strip off the context position of the statements and then
impose a DISTINCT SPO filter on top of that. This is in AST2BOpJoins. But
that is a pretty internal API and is likely to change.
But, no, you would write:
SELECT * {?a ?b ?c}
or
CONSTRUCT ... {?a ?b ?c}
to obtain the default graph for a quad store (RDF merge of all graphs).
If you are using the GRAPH keyword then you are using named graph access
patterns (the name of the named graph is extracted and the RDF merge is not
applied). Not default graph access patterns (the name of the named graph
is not available and an RDF merge is applied).
Bryan
----
Bryan Thompson
Chief Scientist & Founder
SYSTAP, LLC
4501 Tower Road
Greensboro, NC 27410
br...@sy...
http://blazegraph.com
http://blog.bigdata.com <http://bigdata.com>
http://mapgraph.io
Blazegraph™ <http://www.blazegraph.com/> is our ultra high-performance
graph database that supports both RDF/SPARQL and Tinkerpop/Blueprints
APIs. Blazegraph is now available with GPU acceleration using our disruptive
technology to accelerate data-parallel graph analytics and graph query.
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On Mon, Sep 14, 2015 at 6:11 AM, Jean-Marc Vanel <jea...@gm...>
wrote:
> Fine , and thanks ;
>
> this answer is for a SPARQL query,
> but what about the embeded API ?
> Can one access this union graph by API ?
> I guess one accesses this union graph simply by doing this SPARQL query
> by API:
>
> CONSTRUCT {
> ?S ?P ?O
> } WHERE {
> GRAPH ?G {
> ?S ?P ?O
> }
> }
>
> or is there a more efficient way ?
>
> FYI my use case is inferring input forms from ontologies and data in a
> number of named graphs:
>
> https://github.com/jmvanel/semantic_forms/blob/master/scala/forms_play/README.md
>
> Thanks to Banana-RDF, I should be able to support Jena TDB and BlazeGraph
> with the same code.
>
>
>
> 2015-09-14 11:56 GMT+02:00 Bryan Thompson <br...@sy...>:
>
>> Any default graph query in blazegraph has these semantics unless you use
>> FROM to restrict the set of considered graphs.
>>
>>
>> ----
>> Bryan Thompson
>> Chief Scientist & Founder
>> SYSTAP, LLC
>> 4501 Tower Road
>> Greensboro, NC 27410
>> br...@sy...
>> http://blazegraph.com
>> http://blog.bigdata.com <http://bigdata.com>
>> http://mapgraph.io
>>
>> Blazegraph™ <http://www.blazegraph.com/> is our ultra high-performance
>> graph database that supports both RDF/SPARQL and Tinkerpop/Blueprints
>> APIs. Blazegraph is now available with GPU acceleration using our disruptive
>> technology to accelerate data-parallel graph analytics and graph query.
>>
>> CONFIDENTIALITY NOTICE: This email and its contents and attachments are
>> for the sole use of the intended recipient(s) and are confidential or
>> proprietary to SYSTAP. Any unauthorized review, use, disclosure,
>> dissemination or copying of this email or its contents or attachments is
>> prohibited. If you have received this communication in error, please notify
>> the sender by reply email and permanently delete all copies of the email
>> and its contents and attachments.
>>
>> On Mon, Sep 14, 2015 at 5:54 AM, Jean-Marc Vanel <
>> jea...@gm...> wrote:
>>
>>> In Jena TDB there is the special graph urn:x-arq:UnionGraph
>>>
>>>
>>> https://jena.apache.org/documentation/tdb/datasets.html#special-graph-names
>>>
>>> that is the RDF merge of all the named graphs in the SPARQL dataset .
>>>
>>> It is a convenient feature although not standard.
>>>
>>> Is there an equivalent feature in BlazeGraph ?
>>>
>>> --
>>> Jean-Marc Vanel
>>> Déductions SARL - Consulting, services, training,
>>> Rule-based programming, Semantic Web
>>> http://deductions-software.com/
>>> +33 (0)6 89 16 29 52
>>> Twitter: @jmvanel , @jmvanel_fr ; chat: irc://irc.freenode.net#eulergui
>>>
>>>
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>>>
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>>>
>>>
>>
>
>
> --
> Jean-Marc Vanel
> Déductions SARL - Consulting, services, training,
> Rule-based programming, Semantic Web
> http://deductions-software.com/
> +33 (0)6 89 16 29 52
> Twitter: @jmvanel , @jmvanel_fr ; chat: irc://irc.freenode.net#eulergui
>
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