Concurrency control using a new conflict relation

The paper proposes a new conflict relation called preservation. By explicitly including reverse-operations, preservation can be used independently of execution contexts to which different recovery algorithms and/or object models give rise. The paper also makes a two-dimensional (i.e., execution contexts and operations' specifications) comparison between preservation and other conflict relations. In each execution context, a formal comparison reveals that preservation-based concurrency control achieves more concurrency than that which is commutativity-based.