Semantic based concurrency control of open nested transactions in active object oriented database management systems

Active object oriented database management systems (AODBMS) are finding inc reasing application in different application domains and especially for coo perative and long duration activity management. In this paper, we propose a concurrency control mechanism for open nested transactions in an AODBMS. I t exploits the semantics of the transactions to achieve controlled cooperat ion and concurrency among the transactions. Atomic AODBMS transactions are treated as base transactions. A complex transaction type is formed from a c ollection of base and complex transactions, a set of detached mode ECA rule s and a state transition model. The cooperation semantics of a complex tran saction type with other complex transaction types is specified by associati ng with each state of a complex transaction, a set of cooperating complex t ransaction types. The abort semantics of a complex transaction type is spec ified by means of compensating base transactions. We define a correct class of schedule called CoopComp-schedule which satisfies the state transition semantics of the individual complex transactions and also maintains the coo peration and compensation semantics of the individual complex transactions within the generated schedule. A concurrency control scheme called NP-QuadL ock for generating only CoopComp-schedules has been provided. The proof of correctness of the proposed concurrency control mechanism is also given.