  Relational lattice is a formal mathematical model for Relational algebra. It
reduces the set of six classic relational algebra operators to two: natural
join and inner union. We continue to investigate Relational lattice properties
with emphasis onto axiomatic definition. New results include additional axioms,
equational definition for set difference (more generally anti-join), and case
study demonstrating application of the relational lattice theory for query
transformations.
