Flexible transaction dependencies in database systems

Numerous extended transaction models have been proposed in the literature t o overcome the limitations of the traditional transaction model for advance d applications characterized by their long durations, cooperation between a ctivities and access to multiple databases (like CAD/CAM and office automat ion). However, most of these extended models have been proposed with specif ic applications in mind and almost always fail to support applications with slightly different requirements. We propose the Multiform Transaction model to overcome this limitation. The multiform transaction model supports a variety of other extended transacti on models. A multiform transaction consists of a set of component transacti ons together with a set of coordinators which specify the transaction compl etion dependencies among the component transactions. A set of transaction p rimitives allow the programmer to define custom completion dependencies. We show how a wide range of extended transactions can be implemented as multi form transactions, including sagas, transactional workflows, nested transac tions, and contingent transactions. We allow the programmers to define thei r own primitives-having very well-defined interfaces-so that application sp ecific transaction models like distributed multilevel secure transactions c an also be supported.