proposed erratum for SPARQL 1.1 Query Language concerning categorization of ToMultiSet

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proposed erratum for SPARQL 1.1 Query Language concerning categorization of ToMultiSet

Peter F. Patel-Schneider
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