Update semantics for multilevel relations

A formal operational semantics is given for update operations on multilevel relations, i.e., relations in which individual data elements are classified at different levels. For this purpose, the familiar INSERT, UPDATE and DELETE operations of SQL are suitably generalized to cope with polyinstantiation. The authors conjecture that these operations are consistent (or sound) in that all relations which can be constructed will satisfy the basic integrity properties required of multilevel relations. They also conjecture that the operations are complete in that every multilevel relation can be constructed by some sequence of these operations