Hi! I'm using librdf with Virtuoso. It seems that I have successfully built everything but I would like to pose queries directly to Virtuoso and this feature is not working.
According to http://www.openlinksw.com/dataspace/dav/wiki/Main/VirtRDFDriverRedland in order to bypass Rasqal 'vsparql' has to be used as the query language. If I do so, I get no results at all. Is anybody using this feature? thanks in advance Lorena ps: I´m including a small working example based on Redland test.php <?php $world=librdf_php_get_world(); print "<p>Redland world opened\n</p>"; $options = "dsn='Local Virtuoso',user='dba',password='dba'"; $storage_name = "virtuoso"; $name = "http://example.org/salesInstancesSmall#";; # An existing store $storage=librdf_new_storage($world, $storage_name, $name, $options); if(!$storage) die("Failed to create new storage\n"); print "<p>Redland storage created</p>"; $model=librdf_new_model($world,$storage,''); print "<p>Redland model created</p>"; $query = librdf_new_query($world, 'sparql', null, 'PREFIX fn:<http://www.w3.org/2005/xpath-functions#> select distinct(fn:substring-after ( "tatoo", "ta") as ?part) where { ?s ?p ?o}', null); print "<p>Querying : </p>"; $results=librdf_model_query_execute($model, $query); $count=1; while($results && !librdf_query_results_finished($results)) { print "<p> result $count: {"; for ($i=0; $i < librdf_query_results_get_bindings_count($results); $i++) { $val=librdf_query_results_get_binding_value($results, $i); if ($val){ $nval=librdf_node_to_string($val); } else $nval='(unbound)'; print " ".librdf_query_results_get_binding_name($results, $i)."=".$nval; } print "}</p>"; librdf_query_results_next($results); $count++; } if ($results) print "Returned $count results\n"; print "Done\n"; ?> And this is the output produced by the code above: Redland world opened Redland storage created Redland model created Querying : result 1: { part="false"^^} Returned 2 results Done If I replace "sparql" with "vsparql" I get the following output: Redland world opened Redland storage created Redland model created Querying : Done Thanks Lorena On Tue, Mar 20, 2012 at 9:56 PM, lorena <[email protected]> wrote: > As stated here http://librdf.org/docs/api/redland-storage-module-virtuoso.html > > "The Virtuoso Redland RDF Provider is an implementation of the Storage > API, Model and Query interfaces of the Redland framework for RDF. This > provider enables the execution of queries via the Redland Rasqal query > engine or via Virtuoso query engine directly against the Virtuoso > OpenSource Quad Store." > > So I just have to figure out how to skip Rasqal and execute the > queries directly against Virtuoso. > > Any hints would be appreciated > > Lorena > > On Tue, Mar 20, 2012 at 9:40 PM, lorena <[email protected]> wrote: >> Hi: >> >> I'm trying to use librdf to execute SPARQL queries over Virtuoso. >> But, after getting errors trying to use some functions such as >> fn:substring (having the fn prefix declared inside the query) I've >> decided to take a look at Virtuoso's log (after enabling Virtuoso log >> features using trace_on()) >> >> To my surprise, although I successfully retrieve results, some of the >> queries I perform are not logged at all, and other queries are similar >> to the ones I intend to pose but are not the same. >> Moreover, I've tested my queries using Virtuoso Conductor web client >> and they run as expected. >> >> So, my questions are the following: is librdf doing some parsing or >> re-writing on my queries? Is it somehow "loading" the model from >> Virtuoso and using its own querying capabilities to execute my >> queries? If so, how can I skip this step in order to force Virtuoso to >> process the queries? >> >> thanks in advance >> Lorena >> >> -- >> Lorena Etcheverry > > > > -- > Lorena Etcheverry -- Lorena Etcheverry -- Lorena Etcheverry
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