Version-based access capabilities for concurrency control of a database system

Version-based access capabilities (V-capabilities) that can be used for concurrency control of a database system are introduced. A V-capability is an access capability for a version of a data item. If transactions are allowed to access only those versions whose V-capabilities are possessed by them, consistent operation of a database system can be realized by properly controlling the issuance of V-capabilities. Since the issue times of V-capabilities can be different from their use times, V-capabilities add another dimension to the concurrency control of a database system.