On correctness of non-serializable executions

In the standard transaction model, a consistent database state is implicitly defined by assuming that each transaction, when executed in isolation, maps a consistent database state to another consistent database state. In the case of concurrent transaction executions, database consistency is ensured by requiring that the schedule resulting from the concurrent execution of transactions be serializable; that is, equivalent to a serial schedule. Serializability, however, may be too strong a correctness criterion for many applications. In this paper, we develop a theory of non-serializable schedules that preserve database consistency. The cornerstone of our theory is the notion of integrity constraints, in terms of which integrity constraints are defined.