Possible Schedule of Transactions X Schedules That Meet Timing Constraints

This paper presents a technique that is capable of supporting four major requirements for concurrency control in real-time databases: transaction temporal consistency, transaction logical consistency, data temporal consistency, and data logical consistency, as well as tradeoos among these four requirements. The technique is based upon an object-oriented real-time database model in which each object has its own unique con-currency control component. Each concurrency control component deenes a compatibility function where the compatibility of two potential concurrent operations on the object is determined by the semantics of the object, such as allowable imprecision, and by current system conditions, such as time and active operations on the object. The concurrency control component enforces the expressed allowable concurrency through a semantic locking technique. The process of evaluating the compatibility function to grant semantic locks is described, as is the testbed system for this object-based semantic real-time concurrency control technique.