proposed erratum for SPARQL 1.1 Query Language concerning categorization of ToMultiSet

Change table of SPARQL algebra in Section 18.2, moving ToMultiSet from the
Solution Modifiers column to the Graph Pattern column.

Rationale: ToMultiSet produces a multiset of solution mappings, not a
solution sequence.

Effect: This change eliminates a potential problem in the definition of the
exists function where its argument is a ToMulitSet and thus arguably not a
"graph pattern".  This situation occurs in
  SELECT ?x WHERE {
    ?x :p :c .
    FILTER NOT EXISTS { SELECT ?y WHERE { ?y :q :c . } }
  }

The example doesn't make much sense but has been chosen to not exhibit any
cases where EXISTS is otherwise problematic.


Peter F. Patel-Schneider
Nuance Communications

Received on Thursday, 23 June 2016 21:52:46 UTC