| PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> | |
| PREFIX : <http://example/> | |
| PREFIX ex: <http://example/ns#> | |
| # 3 optionals introducing a variable which is not constraint outside. | |
| SELECT * | |
| { | |
| ?x :p ?z | |
| OPTIONAL { ?z :q1 ?w } | |
| OPTIONAL { ?z :q2 ?w } | |
| OPTIONAL { ?z :q3 ?w } | |
| } |