Transactional Composition and Concurrency Control in Disconnected Computing

Composition of software components via Web technologies, scalability demands, and Mobile Computing has led to a questioning of the classical transaction concept. Some researchers have moved away from a synchronous model with strict atomicity, consistency, isolation and durability (ACID) to an asynchronous, disconnected one with possibly weaker ACID properties. Ensuring consistency in disconnected environments requires dedicated transaction support in order to control transactional dependencies between software components and provide a scalable concurrency control mechanism. This paper contributes a simple expression language using Boolean operators to define transactional dependencies and further provides rules to derive an execution semantics that could be exploited by a transaction manager to control the interaction. This work also discusses the use of data classes that demarcate data based on concurrency control related aspects and apply a certain concurrency control mechanism to each class. Such a classification allows better trade-off between consistency needs and the overhead caused by the concurrency control mechanism.