jena throws QueryParsingException on correct but non-standard SPARQL

Question

Hey all,

Using Jena, I frequently run into trouble where I need to run a non-standard sparql that is rejected by Jena's parser, even though it works fine when I submit it manually to Virtuoso's sparql endpoint. For example, the following query works fine on virtuoso:

SELECT ?p, (count (*) as ?count) WHERE { ?s ?p ?o } GROUP BY ?p

and this one too:

SELECT DISTINCT bif:iri_split(?p) WHERE { ?s ?p ?o . } LIMIT 100

But when I run either through Jena I get an exception like this:

  com.hp.hpl.jena.query.QueryParseException: Encountered " "," ", "" at line 1, column 10.
  Was expecting one of:
    <VAR1> ... <VAR2> ... "from" ... "where" ... "{" ...
at com.hp.hpl.jena.sparql.lang.ParserSPARQL11.perform(ParserSPARQL11.java:102)
at com.hp.hpl.jena.sparql.lang.ParserSPARQL11.parse$(ParserSPARQL11.java:53)
at com.hp.hpl.jena.sparql.lang.Parser.parse(Parser.java:37)
at com.hp.hpl.jena.query.QueryFactory.parse(QueryFactory.java:156)

Here is the code I used:

    String endpoint = "http://localhost:8890/sparql";
    String query = "SELECT ?p, (count (*) as ?count) WHERE ?s ?p ?o } GROUP BY ?p";
QueryExecution qe = QueryExecutionFactory.sparqlService(endpoint, query);

I'm using Jena 2.7.4 and Virtuoso OSE 6.1.3127

Can I tell Jena to fore go checking my SPARQL query and just send it straight to Virtuoso? Or is there any other way around this problem?

Accepted Answer

3

SELECT ?p, (count (*) as ?count) WHERE { ?s ?p ?o } GROUP BY ?p

SPARQL does not have "," in select lists.

SELECT DISTINCT bif:iri_split(?p) WHERE { ?s ?p ?o . } LIMIT 100

bif: is virtuoso specific syntax and not in the SPARQL 1.1. grammar. Also, every expression needs an AS and variable name. "Embrace and extend".

You can create a QueryEngineHTTP object directly (used by QueryExecutionFactory.sparqlService) and pass it the query string.

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answered 05 Dec '12, 10:21

AndyS ♦
9.6k●2●7
accept rate: 33%

You're right about the comma, I missed that one. For the other query, unfortunately I'm stuck with using Virtuoso's non-standard extensions. Anyway, using QueryEngineHTTP solves this problem for me!

(05 Dec '12, 12:02) amarillion

Answer 2

2

Another way you can get queries using Virtuoso bif extensions to be seen as valid SPARQL (because as Andy points out they aren't) is to enclose calls to bif functions in < > as if they were URIs. This way standards compliant SPARQL parsers just treat them as IRIs in an unknown scheme and Virtuoso still interprets them as it's extensions e.g.

<bif:iri_split>

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answered 05 Dec '12, 12:10

Rob Vesse ♦
11.8k●6●15
accept rate: 28%

Answer 3

0

To elaborate on AndyS' answer, here is the code that I used in the end:

String endpoint = "http://localhost:8890/sparql";
String query = "SELECT ?p, (count (*) as ?count) WHERE ?s ?p ?o } GROUP BY ?p";
QueryEngineHTTP qe = new QueryEngineHTTP(endpoint, query);
ResultSet rs = qe.execSelect();

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answered 05 Dec '12, 12:03

amarillion
25●4
accept rate: 0%

jena throws QueryParsingException on correct but non-standard SPARQL

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