
Chapter
7:
Foundations
of
Semantic Query Optimization
263
ther. So the only way that FULLY_SUBSUMES could be set to TRUE would
be if one resolvent were a goal clause with only true atoms in the body. But
then, going through the cases (c = c), (ki = ki), as well as GE(c,c) and
LE(c,c), essentially going in the opposite direction to what we did in Case 1,
we find that IC must have subsumed the body of A. But this contradicts the
hypothesis. So FULLY_SUBSUMES is set to FALSE.
Case
2a;
IC and A are not merge compatible.
This means that all the residues are either maximal or redundant. There can
be only one maximal residue, IC+. In this case NOT_MERGE_COM ...