Formal model of correctness without serializabilty

In the classical approach to transaction processing, a concurrent execution is considered to be correct if it is equivalent to a non-concurrent schedule. This notion of correctness is called serializability. Serializability has proven to be a highly useful concept for transaction systems for data-processing style applications. Recent interest in applying database concepts to applications in computer-aided design, office information systems, etc. has resulted in transactions of relatively long duration. For such transactions, there are serious consequences to requiring serializability as the notion of correctness. Specifically, such systems either impose long-duration waits or require the abortion of long transactions. In this paper, we define a transaction model that allows for several alternative notions of correctness without the requirement of serializability. After introducing the model, we investigate classes of schedules for transactions. We show that these classes are richer than analogous classes under the classical model. Finally, we show the potential practicality of our model by describing protocols that permit a transaction manager to allow correct non-serializable executions