- From: Axel Polleres <axel.polleres@deri.org>
- Date: Tue, 5 Oct 2010 16:10:43 -0400
- To: SPARQL Working Group <public-rdf-dawg@w3.org>

http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml In section 8.2 it says: "The other style of negation provided in SPARQL is MINUS which evaluates both its arguments, then calculates solutions in the left-hand side that are not compatible with the solutions on the right-hand side." Isn't this is misleading with respect to the example in Section 8.3 and should rather say ... "The other style of negation provided in SPARQL is MINUS which evaluates both its arguments, then calculates solutions in the left-hand side that either have disjoint domains or are not compatible with the solutions on the right-hand side." On top of that, just for my understanding, in Section 17.4 we say: "The additional restriction on dom(μ) and dom(μ') is added because otherwise if there is a solution mapping in Ω2 that has no variables in Ω1, then Minus(Ω1, Ω2) would be empty, regardless of the rest of Ω2" what does this means on graph G: { :a :p :b; c. :b :p :c} and query SELECT * WHERE { { ?X ?Y ?Z } MINUS { ?A :p ?C OPTIONAL { ?C :p ?X } } } Further: "The empty solution mapping is compatible with every other solution mapping so P MINUS {} would otherwise be empty for any pattern P." I find that sentence a bit confusing. Maybe it would be good to clarify that then as follows: "The empty solution mapping is compatible, but has disjoint domains with every other solution mapping; without the restriction to disjoint domains P MINUS {} would be empty for any pattern P." best, Axel

Received on Tuesday, 5 October 2010 21:50:54 UTC