[Virtuoso-users] SPARQL Conformance

[Thomas Hornung]

Hi,

I have seen in a recent post a question regarding the SPARQL conformance 
of Virtuoso. There you said, that "Virtuoso SPARQL does not match W3C 
recommendation 100%".

Right now I get a parser error message for a query, which is answered by 
other SPARQL engines correctly.

Is the parser error intentional or a bug?

Here the query:

PREFIX rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX dcterms: <http://purl.org/dc/terms/>

SELECT ?name1 ?name2 ?document
FROM <http://my_graph>
WHERE {
  ?document dc:creator ?author1.
  ?author1 foaf:name ?name1.
  OPTIONAL {
    ?document dc:creator ?author2.
    ?author2 foaf:name ?name2.
    FILTER (?author1!=?author2).
  }
}

This is the error message:

*** Error 37000: [Virtuoso Driver][Virtuoso Server]SQ074: Line 17 (...): 
SP031: SPARQL compiler: Variable 'author1' is used in subexpressions of 
the query but not assigned at ';' immediately before end of statement...


Thanks in advance,
Thomas