Classification of weak correctness criteria for real-time database applications

For real-time database systems, transaction processing must satisfy not only logical consistency constraints but also timing constraints. Conflict serializability is too restrictive to achieve the acceptable throughput and predictable response time. Moreover, serializability may not be necessary for concurrent execution and different correctness criteria may be applied to different applications depending on the semantics and the requirements of transactions. We classify the consistency into six forms and propose a relaxed serializability, called statewise serializability, as the weakest form of consistency in our classification. Statewise serializability alleviates the strictness of serializability by allowing for a controlled inconsistent read operation. It can be properly used as a correctness criterion in real-time database applications. We also present the algorithm that determines whether the schedules are statewise serializable, and compare it to other correctness criteria.