To address issues with basic mappings, the paper proposes nested mappings which allow mapping formulas to be arbitrarily nested within each other. The algorithm first computes source and target tableaux representing the schema types and relationships. It then generates basic mappings by pairing tableaux and matching their common elements. Basic mappings are pruned if they are subsumed by or implied by other mappings. A mapping is considered nestable within another if their tableaux and element matches satisfy certain conditions.