[redland-dev] OPTIONAL strangeness

[Danny Ayers]

Either I still don't get OPTIONAL or there's something odd going on
(Rasqal 0.9.10). I'm in a rush to get something finished, haven't got
a test case, but here's an example of something I didn't expect:

This gives me 10 results:

SELECT * WHERE { 
 ?agent foaf:weblog ?blog . 
 ?blog rdfs:seeAlso ?channel . 
} 
LIMIT 10 

This gives me zero results:

SELECT * WHERE { 
 ?agent foaf:weblog ?blog . 
 ?blog rdfs:seeAlso ?channel . 
 OPTIONAL { ?channel rss:title ?name } . 
} 
LIMIT 10 

This gives me 10 results:

SELECT * WHERE { 
 ?agent foaf:weblog ?blog . 
 ?blog rdfs:seeAlso ?channel . 
 ?channel rss:title ?name  . 
} 
LIMIT 10 

The query form/data I'm using is at http://pragmatron.org/query.html

Cheers,
Danny.
-- 

http://dannyayers.com