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  1. Research Projects
Software Reliability


(Diversity In Safety Critical Software)

Principal Investigator: Prof Lorenzo Strigini

Contact: Prof Lorenzo Strigini

Funding to CSR, City University: £150,472

Funding Source: EPSRC Project GR/L07673

Duration: April 1997- 2000

Summary and objectives:

The DISCS project tackles basic issues of interest to the users of design diversity: builders of fault-tolerant, safety-critical, software-based systems, their customers and the agencies responsible for the evaluation and licensing of such systems. The practical aim is better understanding to support better decision-making.
In the long run, better means of designing fault-tolerant systems will make these less expensive in production and will lessen the uncertainty about the fitness for purpose of the eventual product. Better means of evaluation will allow us to place greater confidence in the reliability and safety of systems, and thus better control the societal risk of critical systems.
DISCS is a collaborative project with our sibling centre at the University of Newcastle-upon-Tyne.

Organisation: the work at CSR at City University has focused on reliability modelling for diverse systems: we have extended previous models in various directions: modelling and assessment of a specific system rather than of an 'average' system, consideration of the fault insertion process and of the effects of project management decisions. The results affect product planning (what reliability gains can be expected from using design diversity), development (what project decisions can best achieve effective diversity) and assessment, acceptance and licensing (how to judge the reliability of a specific diverse system). In addition to the practical support for decision-making about diverse software-based systems, this modelling work improves our understanding of issues of diversity, reliability and common-mode failure in a wider context, with possible practical applications in the many other areas of engineering and organisational studies where these issues arise.

In parallel, CSR at Newcastle have concentrated on structuring methods for diverse design. The DISCS project has also interacted with our project DISPO (with the University of Bristol), supporting the use of diversity for nuclear safety.

Results obtained in these projects and in our previous work on diversity are described in the DIVERSITY publications page.

Contributors to the DISCS project at CSR, City University include: Prof Lorenzo Strigini(Principal Investigator), Prof Bev Littlewood, Prof Norman Fenton, Dr Peter Popov, Mr David Wright, Mr Michele Pizza, Ms Eda Marchetti, Mr Andreas Kohn.

Our collaboration with CSR at the University of Newcastle upon Tyne continues with the DOTS project (Diversity with Off-The-Shelf components). Re-use of off-the-shelf components in critical systems usually requires extra measures for assurance of sufficient reliability. Software fault tolerance (diversity) is an attractive measure because it can be applied without changing the internals of the off-the-shelf elements, and at a cost that is still lower than that of bespoke development.

We welcome your feedback, please mail any comments/suggestions to webadm@soi.city.ac.uk
version 2.4 Published: 29th Jun 2004