Disjoint-Interval Topological Sort

The theory of serializability for concurrency control of databases has been extensively studied I: ESWA-76, STEA-76, BERN-79, PAPA-79, SETH-8 11. In this paper, we introduce a unifying concept in the theory, called disjoint-interval topological sort (DITS, for short), -and discuss its applications, including a number of new results. We prove that the existence of a DITS for the transaction IO graph (Section 3) associated with a schdule is a necessary and sufficient condition for serializability. The notion of DITS captures the essence of serializability and most known results on the characterization of serializable schedules follow directly from this main theorem. The most important contributions of the DITS are its appeal to intuition and its wide applicability. It is not only useful as an analysis tool, as we demonstrate in this paper, but it also provides a useful aid to a scheduler [KATO831. The concept of DITS can be easily extended to the multi-version case [STEA-76, MURO-81, BERN-8--82, IBAR-831. REED-791