Enforcing data dependencies in cooperative information systems

Interdependent data are data objects in a cooperative information environment that are related by mutual consistency requirements. A flexible framework for specifying the dependency requirements of interdependent data using data dependency descriptors is discussed. A mechanism called polytransactions is presented to automatically generate actions to restore the consistency between interdependent data. The design of two concurrency control mechanisms for concurrent execution of polytransactions is given. The first is a deadlock-free graph-locking mechanism and the second is a variant of multiversion timestamps with rollback that never rejects operations arriving out of timestamp order. A conceptual system architecture is outlined for the execution of polytransactions. The notion of a multidatabase monitor is discussed