Hello Ivan,
I am sorry. To make the problem easier to spot I simplified our query
somewhat. The original query is as follows:
SELECT ?yr ?name ?document
WHERE {
?class rdf:type foaf:Document.
?document rdf:type ?class.
?document dcterms:issued ?yr.
?document dc:creator ?author.
?author foaf:name ?name.
OPTIONAL {
?class2 rdf:type foaf:Document.
?document2 rdf:type ?class2.
?document2 dcterms:issued ?yr2.
?document2 dc:creator ?author2.
FILTER (?author=?author2 && ?yr2<?yr).
}
FILTER (!bound(?author2)).
}
Here pushing the filter outside the OPTIONAL clause is not a viable option.
Cheers,
Thomas
Ivan Mikhailov schrieb:
Thomas,
Yes, this is an intentional parser error. To make the FILTER condition
meaningful, it should reside outside OPTIONAL, like this:
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) .
}
Variable ?author1 is never bound inside the OPTIONAL clause, so FILTER
(?author1!=?author2) does not differ from
FILTER (?any_unused_variable_name != ?author2) . This is probably not what do
you want.
Semantics of SPARQL FILTER condition differs from semantics of SQL WHERE
condition.
We've decided that error message that violates The Spec is better than running
query that match The Spec in an unusual way.
You can add additional compile-time checks by placing
define sql:signal-void-variables 1
line at the very beginning of the SPARQL statement (before all PREFIX and BASE
declarations if present).
Best Regards,
Ivan Mikhailov,
OpenLink Software.
On Tue, 2008-02-19 at 16:14 +0100, Thomas Hornung wrote:
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
-------------------------------------------------------------------------
This SF.net email is sponsored by: Microsoft
Defy all challenges. Microsoft(R) Visual Studio 2008.
http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
_______________________________________________
Virtuoso-users mailing list
Virtuoso-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/virtuoso-users
--
--------------------------------------------------------------------------
Dipl.-Inf. Thomas Hornung
Institute of Computer Science
Albert-Ludwigs University
Georges-Koehler-Allee, Building 051, Room 01-028
D-79110 Freiburg im Breisgau
phone: +49 (761) 203-8128
fax: +49 (761) 203-8122
e-mail: hornu...@informatik.uni-freiburg.de
web: http://dbis.informatik.uni-freiburg.de/index.php?person=hornungt/
--------------------------------------------------------------------------
