...Overview

This project unifies two previously separate areas of software engineering: design diversity and re-use of off-the-shelf components. It builds on previous research by the Centres for Software Reliability (CSR) at City and Newcastle Universities regarding software reliability modelling, software fault tolerance and structuring of evidence and arguments for dependability assessment. DOTS is a follow-up to the DISCS project (Diversity In Safety Critical Software).

"Commercial-off-the-shelf" (COTS) or, generally, "off-the-shelf" (OTS) software items are increasingly used in building systems, instead of only relying on bespoke software items. A serious problem with OTS items is that they often lack the guarantee of good development practice, and the extensive documentation of it, which are traditionally the basis for accepting/certifying software for critical applications. Fault tolerance via design diversity is an attractive defence against this problem because it may be applied without requiring access to the internals of the OTS item: one can procure one or more additional OTS items with similar functionality, and configure them as, for example, majority-voted system, or, alternatively, the system can be protected against its OTS components by additional components that either monitor it for deviations from its specified behaviour, or for violations of a known "safety envelope" of behaviours that do not endanger the rest of the system. Diversity techniques are good candidates for improving the dependability of OTS items.