Single-level multiversion schedulers for multilevel secure database systems

The concurrency control algorithms used for standard database systems can conflict with the security policies of multilevel secure database systems. The authors describe two new concurrency control algorithms that are compatible with common security policies. They are based on the multiversion timestamp ordering technique, and are implemented with single-level subjects. The use of only single-level subjects cannot introduce any additional threat of compromise of mandatory security; the analysis focuses on correctness. One of these algorithms has been implemented for Trusted ORACLE.<<ETX>>