
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. PatelSchneider
Nuance Communications
