Real-time data semantics and similarity-based concurrency control

This paper formalizes the concept of similarity which has been used on an a d hoc basis by application engineers to provide more flexibility in concurr ency control. We show how the usual correctness criteria of concurrency con trol, namely, final-state, view, and conflict serializability, can be weake ned to incorporate similarity. We extend the weakened correctness criteria in [16] for real-time applications which may run continually, have concurre nt transaction executions, or skip unimportant computations. A semantic app roach based on the similarity concept is then taken to propose a sufficient condition for scheduling real-time transactions without locking of data.