Development of software fault-tolerant applications with Ada95 object-oriented support

Experience has shown that the current software engineering practice is inadequate for producing error-free software. Thus, software fault tolerance (SWFT) must be employed in developing complex safety-critical applications. However, developing applications which are capable of tolerating software errors is a challenging task because the developers have to conquer not only the complexity of the application but also the complexity of fault-tolerance protocols. A middleware which provides SWFT services and establishes a well-defined interface with the application modules will allow the application developer to focus solely on the application complexity. This paper presents such a middleware consisting of reusable SWFT components. It also explores the way these components interface with the application in order to tolerate faults in the application. The paper also reports our experience on using real-time and object-oriented features of the new standard of Ada (Ada95) for implementing the middleware.