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The ISIS Project: R&D Status and Technical Report

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Rept. for 4 May-4 Aug 1985

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This report describes the accomplishments of the ISIS project during the six month period February - August 1985. As reported previously, a prototype version of the ISIS system was completed during the first three months of the project. This software transforms fault-intolerant single-site program specifications into fault-tolerant distributed implementations, and supervises execution of the resulting code. During the second three-month period, several aspects of the system have been enhanced the interface between external programs and resilient objects, the language used to specify resilient objects, and the command language used to control the system. The academic staff designed and begun construction of a performance monitoring tool and some application software. Concurrency is the key to a good performance in a distributed system the less synchronization employed by a system, the less frequently it will experience delays while waiting for inter-site message transmissions to complete. Recently a basic insight into the nature of concurrency in systems like ISIS was achieved. This has led to redesign of the ISIS communication primitives resulting in a communication subsystem that achieves very high levels of concurrency, but at the same time makes it easier to design high-level software that is correct in the presence of failures. The development of these primitives will probably prove to be the most important achievement of the six- month report period. By achieving high levels of concurrency while simultaneously simplifying concurrent algorithms, these represent a breakthrough in the methodology for developing of large, fault-tolerant systems.

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  • Computer Programming and Software

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