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  1. Research
School of Mathematics, Computer Science & Engineering

Diversity

Research on Diversity and Software Fault Tolerance at the CSR

Diversity - background and history

The use of diversity - doing things differently, in two or more ways, to protect against the failures of single procedures - has been ubiquitous in safety-critical industries for decades. In many of these applications, the benefits have been regarded as 'obvious', and it is only in more recent years that there have been formal models and studies of efficacy. Projects at CSR (DISCS, DOTS, the sequence of "DISPO" projects for the UK nuclear safety programme, DIRC, INDEED, SESAMO) have been at the forefront of this research work.

Early studies concerned component redundancy and diversity in hardware systems, and there is a huge literature on common mode faults, beta factors, etc. More recently (in the past 25 years) there has been considerable interest in the use of diversity in software-based systems. A driver for this research was the need for very highly reliable software, coupled with the realisation that there were severe difficulties in making a single version of a program very reliable (e.g. via reliability growth from extensive testing and debugging) (Miller, Morell et al. 1992; Littlewood and Strigini 1993). The use of multi-version software, developed independently and adjudicated at run-time, seemed a possible way out of the difficulties: early work in the field was probably motivated by an analogy with hardware redundancy.

There are some early applications of software diversity that appear to have been successful: examples include critical flight-control computers on Airbus aircraft (Briere and Traverse 1993); various railway signalling and control systems, see e.g. (Hagelin 1988). After experiencing many years of operational use, there seem to be no reports of catastrophic failure of these systems attributable to software design faults.

In spite of these successes as judged after the fact, there have been serious difficulties in assessing the reliability and safety of fault-tolerant diverse systems before deployment - which is precisely the problem faced by a regulator in deciding whether such systems are fit for purpose.

This difficult problem of assessment and prediction of the dependability of design-diverse fault tolerant software-based systems has been the subject of much research - both experimental and theoretical. In several experiments, for example, it has been established that it would be unreasonable to claim that diverse software versions fail independently (Knight and Leveson 1986; Eckhardt, Caglayan et al. 1991): you cannot expect that a 1-out-of-2 system built from channels each having pfds of 10-3 will have a pfd of 10-6. On the other hand, these experiments did show that there was some benefit from the fault tolerance. The Knight and Leveson experiment involved developing 27 versions and subjecting them to 1,000,000 test cases against an oracle version that was presumed correct. On each test case, a vector of 27 dimensions recorded the result - correct or incorrect - of each version. The authors were thus able to calculate the hypothetical reliabilities of fault tolerant architectures comprising different versions. For example, they examined all 2-out-of-3 systems that could be constructed, and found that the average reliability among these was an order of magnitude better than the average reliability of the 27 single versions.

The issue, then, becomes an empirical one. If it is not possible to assume independence of failures, with the resulting simplified mathematics, we need in each case to assess the degree of dependence between the failures of the different versions. This turns out to be very difficult.

References

  • Miller, Morell et al. 1992 - "Estimating the probability of failure when testing reveals no failures." IEEE Trans Software Engineering 18(1).
  • Littlewood and Strigini 1993 - "Assessment of ultra-high dependability for software-based systems." CACM 36(11): 69-80
  • Briere and Traverse 1993 - Airbus A320/A330/A340 Electrical Flight Controls - A Family Of Fault-Tolerant Systems. 23rd International Symposium on Fault-Tolerant Computing (FTCS-23), Toulouse, France, 22 - 24, IEEE Computer Society Press.
  • Hagelin 1988 - Ericsson safety system for railway control. Software Diversity in Computerised Control Systems. U. Voges. Vienna, Springer-Verlag: 11-22.
  • Knight and Leveson 1986 - "Experimental evaluation of the assumption of independence in multiversion software." IEEE Trans Software Engineering 12(1): 96-109.
  • Eckhardt, Caglayan et al. 1991 - "An experimental evaluation of software redundancy as a strategy for improving reliability." IEEE Trans Software Eng 17(7): 692-702.

Contributions of research conducted at the CSR

CSR has made substantial contributions about the modelling, assessment and design issues in diversity and software fault tolerance. Readers can refer to the surveys produced at CSR about diversity for fault tolerance, concerning modelling and assessment, architectural and design issues, and ways for pursuing diversity in developing redundant software components. Recent studies have covered for instance:

Papers produced in CSR on diversity

Papers produced in various projects on diversity and fault tolerance for dependability and security: DISCS, DISPO, DOTS, DIRC, INDEED, ReSIST, SeSaMo and City University London Grants (via the Strategic Development Fund and Pump Priming Fund:

  • Zhao, X., Littlewood, B., Povyakalo, A. A., Strigini, L. & Wright, D. (2017). Modeling the probability of failure on demand (pfd) of a 1-out-of-2 system in which one channel is “quasi-perfect”. Reliability Engineering & System Safety, 158,  pp. 230-245. doi: 10.1016/j.ress.2016.09.002 Full Text
  • Gashi, I., Povyakalo, A. A. & Strigini, L. (2016). Diversity, Safety and Security in Embedded Systems: modelling adversary effort and supply chain risks. Paper presented at the Proceedings of the 12th European Dependable Computing Conference, 5th - 9th September 2016, Gothenburg, Sweden Full Text
  • Bishop, P. G. (2015). Modeling the Impact of Testing on Diverse Programs. Paper presented at the 34th International Conference, SAFECOMP 2015, 23-09-2015 - 25-09-2015, Delft, The Netherlands. Full Text
  • Popov, P. T. (2015). A SAN model for safety and security analysis of the eMotor, an ASIL-D device Full Text
  • Zhao, X., Littlewood, B., Povyakalo, A. A. & Wright, D. (2015). Conservative Claims about the Probability of Perfection of Software-based Systems. Paper presented at the The 26th IEEE International Symposium on Software Reliability Engineering, 02-11-2015 - 05-11-2015, Washington DC, USA. Full Text
  • Gashi, I., Povyakalo, A. A., Strigini, L., Matschnig, M, Hinterstoisser, T & Fischer, B (2014). Diversity for Safety and Security in Embedded Systems. Paper presented at the IEEE International Conference on Dependable Systems and Networks, 23-06-2014 - 26-06-2014, Atlanta, GA, USA Full Text
  • Turkay, C., Mason, S., Gashi, I. & Cukic, B. (2014). Supporting Decision-making for Biometric System Deployment through Visual Analysis. Paper presented at the Reliability and Security Data Analysis (RSDA) Workshop, International Symposium on Software Reliability Engineering, 03-11-2014-06-11-2014, Naples, Italy Full Text
  • Bishop, P. G., Bloomfield, R. E., Littlewood, B., Popov, P. T., Povyakalo, A. A. & Strigini, L. (2014). A conservative bound for the probability of failure of a 1-out-of-2 protection system with one hardware-only and one software-based protection train. Reliability Engineering & System Safety, 130, pp. 61-68. doi: 10.1016/j.ress.2014.04.002 Full Text
  • Bishop, P. G. & Strigini, L. (2014). Estimating Worst Case Failure Dependency with Partial Knowledge of the Difficulty Function. Paper presented at the 33rd International Conference, SAFECOMP 2014, 10-09-2014 - 12-09-2014, Florence, Italy. Full Text
  • Michalas, A. & Komninos, N. (2014). The Lord of the Sense: A Privacy Preserving Reputation System for Participatory Sensing Applications. Paper presented at the 19th IEEE Symposium on Computers and Communication (ISCC’2014), 23rd - 26th June 2014, Madeira, Portugal. Full Text
  • Popov, P. T., Povyakalo, A. A., Stankovic, V. & Strigini, L. (2014). Software diversity as a measure for reducing development risk. Paper presented at the Tenth European Dependable Computing Conference - EDCC 2014, 13 - 16 May 2014, Newcastle upon Tyne, UK. Full Text
  • Cukier, M., Gashi, I., Sobesto, B. & Stankovic, V. (2013). Does Malware Detection Improve With Diverse AntiVirus Products? An Empirical Study. Paper presented at the 32nd International Conference on Computer Safety, Reliability and Security (SAFECOMP), 24- - 27 September 2013, Toulouse, France. Full Text
  • Garcia, M., Bessani, A. N., Gashi, I., Neves, N. & Obelheiro, R. R. (2013). Analysis of operating system diversity for intrusion tolerance. Software: Practice and Experience, doi: 10.1002/spe.2180 Full Text
  • Littlewood, B. & Povyakalo, A. A. (2013). Conservative bounds for the pfd of a 1-out-of-2 software-based system based on an assessor’s subjective probability of “not worse than independence”. IEEE Transactions on Software Engineering, 39(12), pp. 1641-1653. doi: 10.1109/TSE.2013.31 Full Text
  • Littlewood, B. & Povyakalo, A. A. (2013). Conservative reasoning about epistemic uncertainty for the probability of failure on demand of a 1-out-of-2 software-based system in which one channel is “possibly perfect”. IEEE Transactions on Software Engineering, 39(11),  pp. 1521-1530. doi: 10.1109/TSE.2013.35 Full Text
  • Salako, K. & Strigini, L. (2013). When does "diversity" in development reduce common failures? Insights from probabilistic modelling. IEEE Transactions on Dependable and Secure Computing, 11(2),  pp. 193-206. doi: 10.1109/TDSC.2013.32 Full Text
  • Littlewood, B. & Povyakalo, A. A. (2013). Conservative bounds for the pfd of a 1-out-of-2 software-based system based on an assessor's subjective probability of "not worse than independence". IEEE Transactions on Software Engineering. Full Text
  • Salako, K. & Strigini, L. (2013). When does "diversity" in development reduce common failures? Insights from probabilistic modelling. IEEE Transactions on Dependable and Secure Computing, 99, doi: 10.1109/TDSC.2013.32 Full Text
  • Littlewood, B. & Povyakalo, A. A. (2013). Conservative reasoning about epistemic uncertainty for the probability of failure on demand of a 1-out-of-2 software-based system in which one channel is "possibly perfect". IEEE Transactions on Software Engineering, Full Text
  • Bishop, P. G., Bloomfield, R. E. & Cyra, L. (2013). Combining Testing and Proof to Gain High Assurance in Software: a Case Study. Paper presented at the IEEE International Symposium on Software Reliability Engineering (ISSRE 2013), 4 - 7 Nov 2013, Pasadena, CA, USA. Full Text
  • Garcia, M., Bessani, A. N., Gashi, I., Neves, N. & Obelheiro, R. R. (2013). Analysis of operating system diversity for intrusion tolerance. Software: Practice and Experience, doi: 10.1002/spe.2180 Full Text
  • Cukier, M., Gashi, I., Sobesto, B. & Stankovic, V. (2013). Does Malware Detection Improve With Diverse AntiVirus Products? An Empirical Study. Paper presented at the 32nd International Conference on Computer Safety, Reliability and Security (SAFECOMP), 24- - 27 September 2013, Toulouse, France. Full Text
  • Lugini, L., Marasco, E., Cukic, B. & Gashi, I. (2013). Interoperability in Fingerprint Recognition: A Large-Scale Empirical Study. Paper presented at the 43rd Annual IEEE/IFIP International Conference on Dependable Systems and Networks (DSN 2013), 24 - 27 June 2013, Budapest, Hungary. Full Text
  • Gashi, I., Sobesto, B., Mason, S., Stankovic, V. & Cukier, M. (2013). A Study of the Relationship Between Antivirus Regressions and Label Changes. Paper presented at the IEEE International Symposium on Software Reliability Engineering, 4 - 7 Nov 2013, Pasadena, CA, US. - Full Text
  • Strigini, L. & Wright, D. (2013). Bounds on survival probability given mean probability of failure per demand; and the paradoxical advantages of uncertainty. London, UK: Centre for Software Reliability, City University London. Full Text
  • Strigini, L. & Povyakalo, A. A. (2013). Software fault-freeness and reliability predictions. Paper presented at the SAFECOMP 2013, 32nd International Conference on Computer Safety, Reliability and Security, 24 - 27 September 2013, Toulouse, France. Full Text
  • Gashi, I., Stankovic, V., Cukier, M. & Sobesto, B. (2012). Diversity with AntiVirus products: Additional empirical studies. Paper presented at the 42nd IEEE International Conference on Dependable Systems and Networks (DSN) 2012, 25 - 28 June 2012, Boston, USA. Full Text
  • Popov, P. T., Stankovic, V. & Strigini, L.(2012). An Empirical Study of the Effectiveness of 'Forcing Diversity' Based on a Large Population of Diverse Programs. Paper presented at the ISSRE 2012, International Symposium on Software Reliability Engineering, 27 - 30 November 2012, Dallas, Texas, USA. Full Text
  • Kharchenko, V. S., Popov, P. T., Odarushchenko, O. & Zhadan, V. (2012). Empirical evaluation of accuracy of mathematical software used for availability assessment of fault-tolerant computer systems. Reliability: Theory & Applications Full Text
  • Strigini, L. (2012). Fault tolerance and resilience: meanings, measures and assessment. In: K. Wolter, A. Avritzer, M. Vieira & A. van Moorsel (Eds.), Resilience Assessment and Evaluation of Computing Systems. . Berlin, Germany: Springer. Full Text
  • Strigini, L., Bloomfield, R. E., Paulitsch, M. & Reiger, R. (2012). Evidence-Based Security in Aerospace. From Safety to Security and Back Again. Paper presented at the 23rd International Symposium on Software Reliability Engineering (ISSRE 2012), Fast Abstracts Track, 26 - 29 Nov 2012, Dallas, Texas, USA. Full Text
  • Stankovic, V., Bloomfield, R. E., Bishop, P. G. & Gashi, I. (2011). Diversity for Security: a Study with Off-The-Shelf AntiVirus Engines. Paper presented at the 21st International Symposium on Software Reliability Engineering (ISSRE 2011), Hiroshima, Japan. Full Text
  • Garcia, M., Bessani, A. N., Gashi, I., Neves, N. & Obelheiro, R. R. (2011). OS diversity for intrusion tolerance: Myth or reality?. Paper presented at the 41st International Conference on Dependable Systems & Networks (DSN), 27 - 30 Jun 2011, Hong Kong. Full Text
  • Littlewood, B. & Rushby, J. (2011). Reasoning about the Reliability of Diverse Two-Channel Systems in which One Channel is "Possibly Perfect". IEEE Transactions on Software Engineering, doi: 10.1109/TSE.2011.80 Full Text
  • Bishop, P. G., Bloomfield, R. E., Littlewood, B., Povyakalo, A. A. & Wright, D. (2011). Toward a Formalism for Conservative Claims about the Dependability of Software-Based Systems. IEEE Transactions on Software Engineering, 37(5), pp. 708-717. doi: 10.1109/TSE.2010.67 Full Text
  • Popov, P. T. & Strigini, L. (2010). Assessing Asymmetric Fault-Tolerant Software. Paper presented at the Software Reliability Engineering (ISSRE), 2010 IEEE 21st International Symposium on , 1 - 4 Nov 2010, San Jose, California. Full Text
  • Littlewood, B. & Burns, A. (2010). Reasoning About the Reliability of Multi-version, Diverse Real-Time Systems. Paper presented at the 31st IEEE Real-Time Systems Symposium, 30 November - 03 December 2010, San Diego, USA. Full Text
  • Stankovic, V., Bessani, A. N., Daidone, A., Gashi, I., Obelheiro, R. R. & Sousa, P. (2009). Enhancing Fault / Intrusion Tolerance through Design and Configuration Diversity. Paper presented at the 3rd Workshop on Recent Advances on Intrusion-Tolerant Systems (WRAITS 2009), Jun 2009, Estoril, Lisbon, Portugal Full Text
  • I. Gashi, C. Leita, V.Stankovic, O. Thonnard, "An Experimental Study of Diversity with Off-The-Shelf AntiVirus Engines", in Proc. NCA'09, the 8th IEEE International Symposium on Network Computing and Applications, IEEE Computer Society Press, accepted for publication.
  • I. Gashi, P. Popov, V. Stankovic, "Uncertainty Explicit Assessment of Off-The-Shelf Software: A Bayesian Approach", in Elsevier Journal of Information and Software Technology, Elsevier, 51 (2), pp. 497�511, 2009. Abstract
  • M.J.P. van der Meulen, M. A. Revilla, "The Effectiveness of Software Diversity in a Large Population of Programs," IEEE Trans Software Engineering, vol. 34, no. 6, pp. 753-764, Nov./Dec. 2008. Abstract
  • B. Littlewood, P. Popov, L. Strigini, N. Shryane, "Modelling the Effects of Combining Diverse Software Fault Detection Techniques", Formal Methods and Testing: An outcome of the FORTEST Network Revised Selected Papers, (Hierons, R. M., Bowen, J. P., Harman, M., Eds.), vol. LNCS 4949, pp. 345 - 366, Springer, Berlin Heidelberg, 2008. Abstract
  • P. Bishop, I. Gashi, B. Littlewood, D. Wright, "Reliability Modelling of a 1-Out-Of-2 System: Research with Diverse Off-The-Shelf SQL Database Servers", in Proc. ISSRE-2007, 18th International Symposium on Software Reliability Engineering, Trollhattan, Sweden, IEEE Computer Society Press, 2007, pp. 49-58. Abstract
  • I. Gashi, P.Popov, L.Strigini, "Fault tolerance via diversity for off-the-shelf products: a study with SQL database servers", IEEE Transactions on Dependable and Secure Computing, IEEE Computer Society Press, 4(4), 2007, pp. 280-294. Abstract
  • I. Gashi, P.Popov, "Uncertainty Explicit Assessment of Off-the-Shelf Software: Selection of an Optimal Diverse Pair", in Proc. ICCBSS-2007, Sixth International Conference on COTS Based Software Systems, Banff, Alberta, Canada, IEEE Computer Society Press, 2007, pp: 93-102. Abstract
  • K. Salako, "Bounds on the Reliability of Fault-Tolerant Software Built by Forcing Diversity", Computer Safety, Reliability and Security: 26th International Conference, Safecomp 2007, Proceedings, Lecture Notes In Computer Science, (Saglietti F., Oster N., Eds.), pp. 411-416, Springer-Verlag, Nuremberg, 2007. Abstract
  • B. Littlewood, D. Wright, "The use of multi-legged arguments to increase confidence in safety claims for software-based systems: a study based on a BBN of an idealised example", IEEE Trans Software Engineering, vol 33, no 5, pp 347-365, 2007.
  • I. Gashi, P.Popov, "Rephrasing Rules for Off-The-Shelf SQL Database Servers", Proc. 6th European Dependable Computing Conference, 18-20 October 2006, IEEE Computer Society, Coimbra, Portugal, pp:139-148. Abstract
  • V. Stankovic, P.Popov, "Improving DBMS Performance through Diverse Redundancy", Proc. 25th IEEE Symp. on Reliable Distributed Systems (SRDS'06), 2-4 October 2006, IEEE Computer Society, Leeds, UK, pp:391-400. Abstract
  • M.J.P. van der Meulen, L. Strigini, M. Revilla, "On the Effectiveness of Run-Time Checks", Safecomp, 28-30 September 2005, Halden, Norway, (Gran, B.A., Winther, R., Eds.), In print. Lecture Notes in Computer Science, Springer-Verlag.
  • A. Gorbenko, V. Kharchenko, P. Popov, A. Romanovsky, "Dependable Composite Web Services with Components Upgraded Online", in "Architecting Dependable Systems ADS III", (R. de Lemos, C. Gacek, A.Romanovsky, Eds.), vol. LNCS 3549, pp. 96-128 Lecture Notes in Computer Science, Springer-Verlag.
  • L. Strigini, "Fault Tolerance Against Design Faults", in Dependable Computing Systems: Paradigms, Performance Issues, and Applications, (Hassan Diab and Albert Zomaya, Eds.), pp. 21-241, J. Wiley & Sons, 2005. Abstract
  • M.J.P. van der Meulen and M. Revilla, "The effectiveness of Choice of Programming Language as a Diversity Seeking Decision", 5th European Dependable Computing Conference (EDDC-5), Budapest, Hungary, April 2005, (Dal Cin, M., Kaaniche, M., Pataricza, A., Eds.), pp. 199-209, Lecture Notes in Computer Science, Springer-Verlag, 2005.
  • P. Popov and B. Littlewood, "The effect of testing on the reliability of fault-tolerant software", Proc International Conference on Dependable Systems and Networks (DSN2004), pp. 265-274, IEEE Computer Society, 2004. Abstract
  • I. Gashi, P. Popov, V. Stankovic and L. Strigini, "On Designing Dependable Services with Diverse Off-The-Shelf SQL Servers", in Architecting Dependable Systems, (R. de Lemos, C. Gacek and A. Romanovsky, Eds.), pp. 191-214, Lecture Notes in Computer Science, Springer-Verlag , 2004.
  • I. Gashi, P. Popov, and L. Strigini, "Fault diversity among off-the-shelf SQL database servers", Proc. DSN 2004, International Conference on Dependable Systems and Networks, Florence, Italy, 2004, pp. 389-398. Abstract
  • V. Kharchenko, P. Popov and A. Romanovsky,"On Dependability of Composite Web Services with Components Upgraded Online" In Int. Conf. on Dependable Systems and Networks (DSN '04 - Workshop supplement), pages 287-291, Florence, Italy, 2004. Abstract
  • P. Popov, L. Strigini, A. Kostov, V. Mollov and D. Selensky, "Software Fault-Tolerance with Off-the-Shelf SQL Servers", 3rd International Conference on COTS-Based Software Systems (ICCBSS `04), Redondo Beach, California, U.S.A., Lecture Notes in Computer Science, Volume 2959, Springer-Verlag, 2004, pp. 117-126. Abstract
  • J.G.W. Bentley, P.G. Bishop, M.J.P. van der Meulen, "An Empirical Exploration of the Difficulty Function", Safecomp, Potsdam, 21.-24 Sep. 2004, Potsdam, Germany, pp. 60-71, Springer-Verlag.
  • M.J.P. van der Meulen, P.G. Bishop, M. Revilla, "An Exploration of Software Faults and Failure Behaviour in a Large Population of Programs", ISSRE 2004, Rennes, France, pp. 101-12, 2004, Abstract
  • B. Littlewood and L. Strigini, "Redundancy and diversity in security", ESORICS 2004, 9th European Symposium on Research in Computer Security, Sophia Antipolis, France, Springer-Verlag LNCS 3193, 2004, pp. 423-438.
  • L. Strigini, A. Povyakalo and E. Alberdi. "Human-machine diversity in the use of computerised advisory systems: a case study", Proc. DSN 2003, International Conference on Dependable Systems and Networks, San Francisco, U.S.A., 2003, pp. 249-258. Abstract

Other papers on human-machine diversity (medical systems): DIRC mammography case study

  • R. Bloomfield and B. Littlewood, "Multi-legged arguments: the impact of diversity upon confidence in dependability arguments", Proc. DSN 2003, International Conference on Dependable Systems and Networks, San Francisco, U.S.A., IEEE Computer Society, 2003, pp. 25-34. Abstract
  • P. Popov and L. Strigini, "Diversity with Off-The-Shelf Components: A Study with SQL Database Servers", DSN 2003, International Conference on Dependable Systems and Networks - Fast Abstracts supplement, San Francisco, U.S.A., 2003, pp. B84-B85. Abstract
  • P. Popov, L. Strigini, J. May, and S.Kuball, "Estimating Bounds on the Reliability of Diverse Systems", IEEE Transactions on Software Engineering, vol. SE-29, no. 4, 2003, pp.345-359 Abstract.
  • B. Littlewood, P. Popov, L. Strigini, "Assessing the reliability of diverse fault-tolerant software-based systems", Safety Science, vol. 40, pp. 781-796, Pergamon, 2002.
  • P. Popov, "Reliability Assessment of Legacy Safety-Critical Systems Upgraded with Off-the-Shelf Components", SAFECOMP'2002, September 2002, Catania, Italy, Lecture Notes in Computer Science, Springer-Verlag. Abstract.
  • D. Bosio, B. Littlewood, M.J. Newby and L. Strigini. "Advantages of open source processes for reliability: clarifying the issues", Presented at Workshop on Open Source Software Development, Newcastle upon Tyne, February 2002. Abstract
  • B. Littlewood, P. Popov, L. Strigini, "Design Diversity: an Update from Research on Reliability Modelling", Proc. Safety-Critical Systems Symposium 2001, Bristol, UK, Springer-Verlag. Abstract.
  • B. Littlewood, P. Popov, L. Strigini, "Modelling software design diversity - a review", ACM Computing Surveys, Vol. 33, No. 2, June 2001, pp. 177-208. ACM. Abstract.
  • P. Popov, L. Strigini, S. Riddle and A. Romanovsky, "Protective Wrapping of OTS Components", 4th ICSE Workshop on Component-Based Software Engineering: Component Certification and System Prediction, Toronto, May 2001.
  • P. Popov, L. Strigini, S. Riddle and A. Romanovsky, "On Systematic Design of Protectors for Employing OTS Items", 27th Euromicro Conference, Workshop on Component-Based Software Engineering, Warsaw, Poland, 4-6 September 2001, pp. 22-29.
  • B. Littlewood, P. Popov, L. Strigini and Nick Shryane, "Modelling the effects of combining diverse software fault removal techniques", IEEE Transactions on Software Engineering, Vol. SE-26, No. 12, pp.1157-1167, 2000. Abstract.
  • B. Littlewood, P. Popov, L. Strigini, "Assessment of the Reliability of Fault-Tolerant Software: A Bayesian Approach", SAFECOMP'2000, October 2000, Rotterdam, Holland, Lecture Notes in Computer Science, No. 1943, ISBN 3-540-41186-0, pp. 294-308, Springer-Verlag. Abstract.
  • B. Littlewood, P. Popov, L. Strigini, "Assessing the Reliability of Diverse Fault-Tolerant Systems", Proc. INucE International Conference on Control and Instumentation in Nuclear Installations, Bristol, UK, 2000. Abstract.
  • B. Littlewood, "The use of proof in diversity arguments", IEEE Transactions on Software Engineering, Vol. SE-26, No.10, pp.1022-1023, 2000. Abstract.
  • P. Popov, L. Strigini, B. Littlewood "Choosing between Fault-Tolerance and Increased V&V for Improving Reliability", Proc. International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA'2000), pp. 535-540, ISBN 1-892512-22-x, June 26-29, 2000, Monte Carlo Resort, Las Vegas, Nevada, USA. Abstract.
  • B. Littlewood, P. Popov, L. Strigini, "N-version Design Versus one Good Version", Proc. International Conference on Dependable Systems and Networks DSN'2000 (FTCS-30, DCCA-8) - Fast Abstracts, New York, USA, 2000, p. B42-B43. Abstract.
  • P. Popov, L. Strigini and A. Romanovsky, "Diversity for off-the-shelf Components", Proc. International Conference on Dependable Systems and Networks DSN'2000 (FTCS-30, DCCA-8) - Fast Abstracts, New York, USA, 2000, p. B60-B61.
  • L. Strigini, B. Littlewood, "A discussion of practices for enhancing diversity in software designs", Centre for Software Reliability, Technical Report LS_DI_TR_04, 2000. Abstract.
  • B. Littlewood, P. Popov, L. Strigini, "A note on modelling functional diversity", "Reliability Engineering an System Safety", 66, (1999), pp. 93-95. Abstract.
  • P. Popov, L. Strigini and A. Romanovsky, "Choosing Effective Methods for Design Diversity - How to progress from Intuition to Science", 18th International Conference, SAFECOMP'99, held in Toulouse, France, September 1999. "Lecture Notes in Computer Science series", No. 1698, ISBN 3-540-66488-2, pp. 272-285, Springer-Verlag. Abstract.
  • P. Popov, L. Strigini, "The Reliability of diverse systems: a contribution using modelling of the fault-creation process", Centre for Software reliability, Technical report, City University, 1999. Abstract.
  • P. Popov and L. Strigini, "Conceptual Models for the Reliability of Diverse Systems - New Results", FTCS'28, Munich, Germany, June 1998. Abstract.
  • P. Popov, L. Strigini and M. Pizza, "The efficacy of Design Diversity against Design Error: some practical considerations", 3rd International Conference on Control & Instrumentation in Nuclear Installations, Edinburgh, 12-14 May, 1998. Abstract.
  • M. Pizza, L. Strigini, "Comparing the effectiveness of testing methods in improving programs: the effect of variations in program quality", Proc. 9th International Symposium on Software Reliability Engineering, ISSRE'98, Paderborn, Germany, IEEE Computer Society Press, 1998, p. 144-153. More can be found Abstract.

Previous papers by researchers of CSR at City, University of London (in chronological order):

  • P.G. Bishop, "Project on Diverse Software "An Experiment in Software Reliability", in Proc. 4th IFAC Workshop SAFECOMP'85, Como, Italy, 1985, pp. 153-158.
  • L. Strigini and A. Avizienis, " Software Fault-Tolerance and Design Diversity: Past Experience and Future Evolution", in Proc. 4th IFAC Workshop SAFECOMP'85, Como, Italy, 1985, pp. 167-172.
  • P.G. Bishop, D.G. Esp, M. Barnes, P. Humphreys, G., Dahll, J. Lahti, "PODS-A Project on Diverse Software", IEEE Trans. Software Engineering, vol. SE-12, no. 19, 1986, pp. 929-941.
  • P.G. Bishop, "The PODS Diversity Experiment", in Dependable Computing and Fault Tolerant Systems, Vol. 2, (ed. U. Voges), Springer Verlag, ISBN 0-387-82014, New York-Wien, 1987, pp 51-84.
  • B. Littlewood and D. R. Miller, "A conceptual model of multi-version software", in Proc. 17th International Symposium on Fault-Tolerant Computing (FTCS-17), Pittsburgh, Pennsylvania, 1987, pp. 150-155.
  • B. Littlewood and D. R. Miller, "A conceptual model of the effect of diverse methodologies on coincident failures in multi-version software", in Proc. 3rd International GI/ITG/GMA Conference on Fault-Tolerant Computing Systems, Bremerhaven, Germany, 1987, pp. 263-272.
  • P.G.Bishop, F.D. Pullen, "PODS Revisited - A Study of Software Failure Behaviour", Eighteenth Fault Tolerant Computing Symposium (FTCS-18),Tokyo, June, IEEE Computer Society Press, ISBN 0-8186-0867-6, 1988, pp. 2-8.
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version 2.26 Published: 2nd Feb 2011