[Rdfapi-php-interest] SPARQL OPTIONAL error

[Sergey C. <rdf...@an...>]

It looks like RAP is having a significant issue with handling OPTIONAL
blocks - when variable from mandatory part is also used within OPTIONAL
block and non-optional part of the query matches nothing, OPTIONAL block
still gets executed as if there was no mandatory part of the query.

For example, query like this:
*PREFIX dc: <http://purl.org/dc/elements/1.1/>*
*PREFIX foaf: <http://xmlns.com/foaf/0.1/>*
*SELECT ?blog, ?title WHERE {*
*<http://www.sergeychernyshev.com/sergey> foaf:weblog ?blog .*
*OPTIONAL { ?blog dc:title ?title}*
*}*

ran against http://www.sergeychernyshev.com/sergey.rdf (where foaf:weblog
triple exists) works fine and returns one entry with defined ?blog and empty
?title.

But query
*PREFIX dc: <http://purl.org/dc/elements/1.1/>*
*PREFIX foaf: <http://xmlns.com/foaf/0.1/>*
*SELECT ?blog, ?title WHERE {*
*<http://www.w3.org/People/Berners-Lee/card#i> foaf:weblog ?blog .*
*OPTIONAL { ?blog dc:title ?title}*
*}*
ran against http://www.sergeychernyshev.com/profile/tests/timbl.rdf (where
no foaf:weblog triples exist) returns ?blog variables bound to all subjects
that have dc:title properties as if this query was ran
*PREFIX dc: <http://purl.org/dc/elements/1.1/>*
*PREFIX foaf: <http://xmlns.com/foaf/0.1/>*
*SELECT ?blog, ?title WHERE {*
*OPTIONAL { ?blog dc:title ?title}*
*}*

I don't even know how to approach this! Will appreciate any help.

Thank you,

          Sergey


-- 
Sergey Chernyshev
http://www.sergeychernyshev.com/