Thanks for your prompt reply. I see what you are saying, so I tried:
tdbloader —set http://jena.hpl.hp.com/TDB#unionDefaultGraph=true
—loc=TDBLocation —graph=‘<graph/named#graphName1>’ rdfFile.ttl
then tried to query it:
“PREFIX GRAPH: <graph/named#> SELECT * FROM NAMED graph:graphName1 WHERE{ GRAPH
graph:graphName1 {?s ?p ?o} }”
But still receive an empty result set. So two questions remain:
1. Am I not creating the absolute URI correctly?
2. Is there a commonly used base URI for named graphs that I could be
using or should I just make my own as I tried to do?
Thanks,
Brad
On Feb 18, 2014, at 4:29 AM, Andy Seaborne <[email protected]> wrote:
> On 18/02/14 00:35, Brad Moran wrote:
>> Hi,
>>
>> I am loading data into a TDB as named graphs via command line tdbloader
>> utility with unionDefaultGraph flag specified true for example:
>>
>> tdbloader —set http://jena.hpl.hp.com/TDB#unionDefaultGraph=true
>> —loc=TDBLocation —graph=‘graphName1’ rdfFile.ttl
>> tdbloader —set http://jena.hpl.hp.com/TDB#unioncDefaultGraph=true
>> —loc=TDBLocation —graph=‘graphName2’ rdfFile2.ttl
>>
>> Then I can successfully query to get everything from the union graph with
>> the following SPARQL:
>> “SELECT ?s ?p ?o ?g WHERE{ GRAPH ?g{ ?s ?p ?o} }"
>>
>> But now I want to query for data from just one of the named graphs. From the
>> SPARQL tutorial in Jena documentation I tried:
>>
>> “SELECT ?s ?p ?o FROM NAMED <graphName1> WHERE{ GRAPH <graphName1> {?s
>> ?p ?o} }”
>>
>> However, it returns 0 results.
>>
>> I also tried:
>>
>> “SELECT ?s ?p ?o FROM NAMED <graphName1> WHERE{ ?s ?p ?o }”
>>
>> and
>>
>> “SELECT ?s ?p ?o WHERE{ GRAPH <graphName1> {?s ?p ?o} }”
>>
>> and
>>
>> “SELECT ?s ?p ?o ?g FROM NAMED <graphName1> WHERE{ GRAPH ?g {?s ?p ?o}
>> }”
>>
>> But none of the queries produce any results. I am wondering if maybe setting
>> the flag unionDefaultGraph to true is incorrect for my purpose? I want to be
>> able to query all graphs at once, but also be able to query individual named
>> graphs.
>>
>> Thanks,
>> Brad
>
> This is not related to unionDefaultGraph.
>
> When the SPARQL parser sees
>
> SELECT * FROM NAMED <graphName1> WHERE{ GRAPH ?g {?s ?p ?o} }
>
> then <graphName1> will be resolved against the base URI. There is always a
> base URI but if you don't specify it it is something unhelpful like the file:
> URI of the current directory.
>
> The loader, seeing —graph="graphName1", isn't going near a parser so that is
> the URI and it is not resolved. The URI is just "graphName1" and does not
> match <graphName1>
>
> Example:
> Printing queries respects implicit the base URI so it get turned back into
> <g> but the algebra printing does not
>
> qparse --print=op 'SELECT * { GRAPH <g> { ?s ?p ?o } }'
>
> which gives, for me:
>
> (graph <file:///home/afs/g>
> (bgp (triple ?s ?p ?o)))
>
> <g> ==> <file:///home/afs/g>
>
>
> Use an absolute URI for the graph name in tdbloader operation and a prefix in
> the query to make the GRAPH .. look nice.
>
> Andy
>
