Thomas, I've also tried to write the query in pure SPARQL but failed. I'm afraid that in that case you need SPARQL-BI extensions, not pure SPARQL. 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 ?yr ?name ?document WHERE { ?document rdf:type ?class ; dc:creator ?author ; dcterms:issued ?yr . ?class rdf:type foaf:Document . ?author foaf:name ?name . { select ?author (min (?yr2)) as ?yr where { ?document2 rdf:type ?class2 ; dc:creator ?author ; dcterms:issued ?yr2 . ?class2 rdf:type foaf:Document } } } Or even shorter (but more obfuscated) SELECT ?yr ?author+>foaf:name ?document WHERE { ?document a [ a foaf:Document ] ; dc:creator ?author ; dcterms:issued ?yr . { select ?author (min (?document2+>dcterms:issued)) as ?yr where { ?document2 a [ a foaf:Document ] ; dc:creator ?author } } } Note: I've written these queries but not tested. Best Regards, Ivan Mikhailov, OpenLink Software. On Thu, 2008-02-21 at 17:09 +0100, Thomas Hornung wrote: > 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/ > -------------------------------------------------------------------------- >
