Concurrent Pascal with backward error recovery: Language features and examples

The programming language Concurrent Pascal has been extended to include some language features that facilitate the writing of fault-tolerant software. As a result, it is possible now to (1) write operating systems with a measure of fault-tolerance, and (2) for such an operating system to support fault-tolerant user programs. The paper describes these language features and illustrates their use with the help of a few working examples.     

Formalization of an architectural model for exception handling coordination based on CA action concepts

Architectures based on Coordinated Atomic action (CA action) concepts have been used to build concurrent fault-tolerant systems. This conceptual model combines concurrent exception handling with action nesting to provide a general mechanism for both enclosing interactions among system components and coordinating forward error recovery measures. This article presents an architectural model to guide the formal specification of concurrent fault-tolerant systems. This architecture provides built-inCommunicating Sequential Processes (CSPs) and predefined channels to coordinate exception handling of the user-defined components. Hence some safety properties concerning action scoping and concurrent exception handling can be proved by using the FDR (Failure Divergence Refinement) verification tool. As a result, a formal and general architecture supporting software fault tolerance is ready to be used and proved as users define components with normal and exceptional behaviors.     

Distributed control system data base updating and error recovery

Distributed data acquisition and control systems are envisioned as the solution to objectives sought for a long time: reliable online systems which degrade gracefully. Critical applications however require a great deal of communication of both commands and data which in turn leads to distributed data bases and their attendant problems. The most critical software problem in such systems is error recovery because of the many modes of failure which may occur. Software architecture which leads to feasible distrubuted system errir recovery is discussed, including atomic transactions, intention lists, and controlled data sets.     

基于PC的直线度误差自动测量与评定系统

介绍了一种新颖的直线度误差自动测量系统———便携式激光准直仪。直线度误差评定软件设计时 ,考虑了直线度误差的两类测量方法和两种评定方法 ,具有运算速度快、适合直线度误差测量仪器多等特点