Interval sets and interval-set algebras

An interval set is an interval in the power set lattice based on a universal set and is a family of subsets of the universal set. Interval sets and interval-set algebras provide a tool for modeling and processing partially known concepts and for approximating undefinable or complex concepts. Existing results on interval sets and interval-set algebras are reviewed and new results are given. Two types of interval-set algebras are examined based on an inclusion ordering and a knowledge ordering, respectively. Related studies are summarized.