The Impact of Concurrency Control on the Programming Model of ConTracts

The ConTract model has been developed to extend the scope of classical (ACID)transactions to long-running executions such as workflows. A particular important aspect of the ConTract model is its approach to concurrency control. It uses semantic rather than syntactic synchronization, which influences both the programming style of long-running applications and the architecture of a ConTract processing system. This paper will give an overview of the major aspects of the concurrency control approach of ConTracts. It will explain how applications can use the predicate based synchronization mechanism. Fur thermore, the corresponding programming model will be introduced and a short introduction into the implementation is presented..

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