Analysis of Dependencies in Advanced Transaction Models

Transactional dependencies play an important role in coordinating and executing the sub-transactions in advanced transaction processing models, such as, nested transactions and work-flow transactions. Researchers have formalized the notion of transactional dependencies and have shown how various advanced transaction models can be expressed using different kinds of dependencies. Incorrect specification of dependencies can result in unpredictable behavior of the advanced transaction, which, in turn, can lead to unavailability of resources and informa-tion integrity problems. In this work, we focus on how to correctly specify dependencies in an advanced transaction. We enumerate the different kinds of dependencies that may be present in an advanced transaction and classify them into two broad categories: event ordering and event enforcement dependencies. Different event ordering and event enforcement dependencies in an advanced transaction often interact in subtle ways resulting in conflicts and redundancies. We describe the different types of conflicts that can arise due to the presence of multiple de-pendencies and describe how one can detect such conflicts. An advanced transaction may also contain redundant dependencies – these are dependencies that can be logically derived from other dependencies. We show how such extraneous dependencies can be eliminated to get an equivalent set of dependencies that has the same effect as the original set. Our dependency analysis is done in the context of a generalized advanced transaction model that is capable of expressing different kinds of advanced transactions. 1

Automated analysis of dependencies in advanced transaction models

Researchers have formalized the notion of transactional dependencies and shown how these dependencies can be ordered and combined in such a way as to express various advanced transaction models. The problem has been that both the complexity of these models and the way in which the dependencies interact can make manual analysis cumbersome and error-prone. In this vein, this work enumerates fifteen different dependencies that are often found in such models. Using the given dependencies, transaction models can be built; however, the models must be checked for three different issues: redundant, conflicting, and “ignored ” dependencies. These issues are described in the context of multiple dependencies per a subtransaction as well as over the course of multiple subtransactions. An automated technique for checking any given model that will attempt to simplify the model and detect both conflicts and superfluous dependencies is also described. 1