On the complexity of concurrency control using semantic information

In the presence of semantic information, serializability is too strong a correctness criterion and unnecessarily restricts concurrency. Many researchers have investigated the use of semantic information to allow interleaving among transactions which are non-serializable, but which nonetheless preserves the consistency of the database and is acceptable to the users. In this paper we consider a class of schedules, calledconflict-correct schedules, first proposed by Farrag and Özsu, which enlarges upon the class of serializable schedules by taking semantic information of transactions into account. In this paper we show that the problem of recognizing schedules in this class is NP-complete. Thus it is unlikely that there exists an efficient scheduler which accepts the entire class of conflict-correct schedules.