Semantic serializability: A correctness criterion for processing transactions in advanced database applications

Serializability requires that the execution of each transaction must give t he illusion to be an atomic action, i.e., the execution of a set of transac tions must appear to be a serial one. This requirement, however, is too str ong and unnecessarily restricts concurrency among transactions, when semant ic information is available for the transaction processing mechanism. In th is paper, a new correctness criterion for concurrent execution of database transactions, denoted semantic serializability, is proposed. Semantic seria lizability is based on the use of semantic information about database objec ts (and not about transactions). The main idea of our proposal is to provid e different atomicity views for each transaction and, for this reason, to a llow interleavings among transactions which are nonserializable, but which preserve database consistency. We develop two concurrency control protocols , which are based on semantic serializability. One protocol is based on a l ocking-mechanism and the other one uses a non-locking approach. Our proposa l is suitable to a wide variety of advanced database applications, such as CAx, MDBS, GIS and WFMS. (C) 1999 Elsevier Science B.V. All rights reserved .