A System for Specifying and Coordinating the Execution of Reliable Distributed Applications

An increasing number of distributed applications are being constructed by composing them out of existing applications. The resulting applications can be very complex in structure, containing many temporal and dataflow dependencies between their constituent applications. An additional complication is that the execution of such an application may take a long time to complete, and may contain long periods of inactivity, often due to the constituent applications requiring user interactions. In a distributed environment, it is inevitable that long running applications will require support for fault-tolerance and dynamic reconfiguration: machines may fail, services may be moved or withdrawn and application requirements may change. In such an environment it is essential that the structure of applications can be modified to reflect these changes. This paper describes the design and implementation of a coordination language and the supporting execution environment for expressing the run-time co..