On Well-Behaved Semantics Suitable tor Aggregation

In this paper we study semantics WFS
0
, WFS
1
for DATALOG programs by extending the calculus of Brass and Dix ([1, 2]) with more transformation rules. These extended calculi still share the same nice properties as the base calculus: they are confluent and terminating. In addition, WFS
0
is rational, well-behaved and polynomial-time computable. Even more important, our experiments suggest that such semantics can be used for potential applications in modelling aggregation in deductive databases. Previous work has been done by the second author recently ([3]).