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Fwd: SPARQL Bindings Example on W3C WD

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Thu, 14 Jul 2011 14:59:55 +0100
Message-ID: <4E1EF65B.40105@epimorphics.com>
To: SPARQL Working Group <public-rdf-dawg@w3.org>
Pre LC comment:

-------- Original Message --------
Subject: 	SPARQL Bindings Example on W3C WD
Date: 	Thu, 14 Jul 2011 20:13:44 +0700
From: 	Fariz Darari

	

	

...

I am interested in SPARQL and am using it in my Semantic Web project, 
especially the Federated Query feature. I have read the SPARQL Federated 
Query extension specification 
(http://www.w3.org/2009/sparql/docs/fed/service). I have been wondering 
of the BINDINGS operative query example:

PREFIX : <http://example.org/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?s ?o1 ?o2
{
   ?s ?p1 ?o1
   OPTIONAL { SERVICE <http://example.org/sparql> {?s foaf:knows ?o2 }}
} BINDINGS ?o2 {
  (:b)
}

Shouldn't it give the resulting sequence like below?

so1o2
<http://example.org/a>"alan@example.org 
<mailto:alan@example.org>"<http://example.org/b>
<http://example.org/a>"Alan"<http://example.org/b>
<http://example.org/a>"bob@example.org 
<mailto:bob@example.org>"<http://example.org/b>
<http://example.org/a>"Bob"<http://example.org/b>
<http://example.org/c>"alice@example.org 
<mailto:alice@example.org>"<http://example.org/b>
<http://example.org/c>"Alice"<http://example.org/b>

I think that it's the OPTIONAL keyword that makes the result like that.
...

Best regards,
Fariz Darari
Received on Thursday, 14 July 2011 14:00:38 GMT

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