This three-year award supports U.S.-Italy collaborative research in database security between Sushil Jajodia, George Mason University, and Elisa Bertino, University of Milan, Italy. The objective of their research is to produce flexible mechanisms that could be used to improve access controls in commercial database management systems. Jajodia brings to the collaboration expertise in the multilevel relational data model and Bertino, a thorough background in object-oriented database systems, composite objects, and authorization for next-generation database systems. The joint research will examine issues related to access controls in relational databases and in object-oriented data bases, such as negative and conflicting authorizations, modeling multilevel entities, secure garbage collection mechanisms, polyinstantiation, and discretionary authorization.