The basic transaction model has evolved over time to incorporate more complex transactions structures and to take the advantage of semantics of higher-level operations that cannot be seen at the level of page reads and writes. Well known examples of such extended transaction models include nested and multi-level transactions. A number of relaxed transaction models have been defined in the last several years that permit a controlled relaxation of the transaction isolation and atomicity to better match the requirements of various database applications. Correctness criteria other than global serializability have also been proposed. Several examples of extended/relaxed transaction models are reported in . Recently, transaction concepts have begun to be applied to support applications or activities that involve multiple tasks of possibly different types (including, but not limited to transactions) and executed over different types of entities (including, but not limited to DBMSs). The designer of such applications may specify inter-task dependencies to define task coordination requirements, and (sometimes) additional requirements for isolation, and failure atomicity of the application. We will refer to such applications as multi-system transactional workflows. While such workflows can be developed using ad hoc methods, it is desirable that they maintain at least some of the safeguards of transactions related to the correctness of computations and data integrity.
Sheth, A. P.,
& Rusinkiewicz, M.
(1993). On Transactional Workflows. Data Engineering Bulletin, 16 (2), 20-25.