Content area
Autonomy and Security are two major concerns in an open distributed system. Interoperation is enabled by distributed transaction processing because transactions ensure reliable and consistent information sharing. It is highly desirable to provide secure transaction accesses in an autonomous environment. In this thesis we consider the effect of autonomy and security on distributed transaction processing.
Relating to the dimension of autonomy, we consider reliable distributed transaction processing in multidatabase systems. A multidatabase system (MDBS) allows organizations within the federation to benefit from information sharing while still maintaining their autonomy. Our approach is reliable in the sense that it ensures correct execution in the face of failures. We show necessary and sufficient conditions for supporting reliable transaction management in MDBSs. Our work considers an MDBS composed of single-version or multiversion local database systems. We show that our transaction management scheme not only ensures global serializability in the face of failures, but also ensures freedom from global deadlocks.
Next we extend our work to cover the nested transaction model. Nested transactions are more flexible and robust than classical flat transactions in a distributed environment. We show a correctness theorem for nested transactions based on one-copy serializability. Our work supports global nested transactions under the constraint that LDBSs support only flat transactions. We introduce a deferred-update approach to replace the need for atomic commitment protocols. We also present a reliable nested transaction processing protocol for MDBSs.
Related to the dimension of security, we consider distributed transaction management for multilevel secure (MLS) replicated database systems. Multilevel secure systems provide strong mechanisms for controlling the disclosure of sensitive information. We identify an incomparably-acyclic property that avoids inconsistency problems in previous work. We present two transaction processing protocols for MLS replicated database systems and demonstrate their correctness.
Finally, we consider both autonomy and security: We consider concurrency control problems in federated multilevel secure database systems where autonomy and security are of paramount importance. We identify issues and constraints for transaction processing in such settings. We present a secure validation protocol that ensures correctness and conforms to our autonomy and security requirements.