Programming cheaper dependable systems

Services must be dependable if they are to deliver the benefit that justifies the cost of deploying them. Services must be sufficiently dependable for their purpose, but no more costly than is necessary to achieve that level of dependability. This document describes some work on identifying programming concepts that can be exploited to reduce the cost of dependable systems. This includes both the reduction of operating cost by identifying where cheaper mechanisms are acceptable, and reducing the cost of developing dependable systems by providing guidance to programmers and tools to support the proposed programming strategy. The main theme is to explore the issue of mutability in the context of dependable systems. The objective is to identify potential benefits of a better understanding of mutability, in particular, the benefits of a better ability to propagate information about mutability. Once the benefits have been identified, it will be possible to specify the mechanisms required to achieve those benefits. It will then be possible to develop guidelines for the design and implementation of systems so as to make the best use of the mechanisms. These will form part of the methodology for dependability. The work is being conducted as part of ANSA Phase III task D2 Programming cheaper dependable systems