wrong example in the Fed.Ext. document


The example in Section 2.1 of the Federation Extensions document [1] uses the 
void vocabulary wrongly. The default graph in this example contains RDF 
triples such as

  <http://GABABR1.example/SPARQL> a void:Dataset ;
                              dcterms:subject entrez:h2550 .

The variable ?service of the example query is then mapped to URI 
<http://GABABR1.example/SPARQL> and this URI is then used to identify a
SPARQL service. That's not the meaning of void:Dataset. void:Dataset refers
to a linked dataset and not to a SPARQL endpoint that exposes a linked 
I propose to adjust the example as follows:

1.) replace the abovementioned triples by the following (similar for the other 
SPARQL services):

  <http://GABABR1.example/dataset> a void:Dataset ;
                  dcterms:subject entrez:h2550 ;
                  void:sparqEndpoint <http://GABABR1.example/SPARQL> .

2.) replace the first triple patterns in the sample query by the following:

  # Find the service with the expertise.
  ?dataset dcterms:subject ?gene ;
                 void:sparqEndpoint ?service .
  FILTER (?gene = entrez:h2550 || ?gene = entrez:h9568)

BTW, the FILTER clause in the current example lacks a closing bracket.


[1] http://www.w3.org/TR/2010/WD-sparql11-federated-query-20100601/

Received on Friday, 4 June 2010 12:38:50 UTC