  The use of aggregates in recursion enables efficient and scalable support for
a wide range of BigData algorithms, including those used in graph applications,
KDD applications, and ML applications, which have proven difficult to be
expressed and supported efficiently in BigData systems supporting Datalog or
SQL. The problem with these languages and systems is that, to avoid the
semantic and computational issues created by non-monotonic constructs in
recursion, they only allow programs that are stratified with respect to
negation and aggregates. Now, while this crippling restriction is
well-justified for negation, it is frequently unjustified for aggregates, since
(i) aggregates are often monotonic in the standard lattice of set-containment,
(ii) the PreM property guarantees that programs with extrema in recursion are
equivalent to stratified programs where extrema are used as post-constraints,
and (iii) any program computing any aggregates on sets of facts of predictable
cardinality tantamounts to stratified programs where the precomputation of the
cardinality of the set is followed by a stratum where recursive rules only use
monotonic constructs. With (i) and (ii) covered in previous papers, this paper
focuses on (iii) using examples of great practical interest. For such examples,
we provide a formal semantics that is conducive to efficient and scalable
implementations via well-known techniques such as semi-naive fixpoint currently
supported by most Datalog and SQL3 systems.
