Seminar: Software Maintenance: Legacy and Archaeology

  Event description   Programme    


Software Maintenance: Legacy and Archaeology

Thursday 6 May, 2021 - Zoom

This seminar considers the issue of software maintenance in a safety context: the process, the code and documentation changes, and the verification. Much legacy software is not properly documented and historically poorly maintained, even though it may be performing a safety-related function. Often we are presented with a partial or incomplete picture of the design and code and yet changes have to be made. What are the best strategies to use? How much "software archaeology" must be undertaken to understand what is there and what it does? How much of the current usage must be understood for a safe change to be made? How should we test if we are not sure of all the functionality?

The speakers at this event will consider these questions and others in an attempt to devise sound methods for tackling change to legacy code.

Speakers include:

Rod Chapman, Protean Code Ltd - Modern verification meets old code...

Chris Hobbs, Blackberry QNX - But I only changed 5 lines of code!

Peter Niemann, CGI - Still improving after 20 years of maintenance

Simon Scutt, Thales - It was never designed to do that!

This event is free to SCSC members, see

Presenter and talk details:

Rod Chapman, Protean Code Ltd

Roderick Chapman is an independent consultant software engineer. He specialises in the development of safety and security-critical systems, from requirements engineering, through architectural design and implementation, to verification, audit and assessment. Following graduation from the University of York, Rod joined Praxis (now Capgemini Engineering UK), and contributed to many of the company’s keynote projects, rising to the role of principal engineer for software process and design. He also led the programming language and verification research group at Praxis, leading the technical development, training, sales and marketing of the SPARK product line. Rod is a regular speaker at international conferences, and is widely recognized as a leading authority on high-integrity software development, programming language design, and software verification tools. In 2006, he was invited to become a Fellow of the British Computer Society. In 2011, Rod was the joint recipient of the inaugural Microsoft Research Verified Software Milestone Award for his contribution to the Tokeneer project. In February 2015, Rod was appointed Honorary Visiting Professor in the Department of Computer Science at the University of York.


This talk will look at what contemporary technology and development practices can bring to maintenance of long-lived or "legacy" software systems. Modern times have brought us almost unimaginable computing resource, formal verification tools, agile methods, and many more great ideas, but how can these be deployed for long-lived systems? This talk will go over how some of these ideas can be exploited, based on experience with developing some long-lived software systems, retiring them, and bringing them back to life.

Chris Hobbs, Blackberry QNX

Chris first met the implications of Safety-Critical software in 1986 when he was asked to sign off a system where the dangerous situation was "extremely unlikely" to occur. For the last 12 years he has worked for BlackBerry QNX on the safety certification of low-level, embedded code and now believes he is now getting close to knowing how he should have reacted in 1986. He is the author of several books including "Flying Beyond --- The Canadian Commercial Pilot Textbook"  and "Embedded Software Development for Safety Critical Systems". Outside the safety world, Chris is a keen pilot and enthusiastic singer of Schubert Lieder


Over the last few years there has been an increased focus on arguing "proven-in-use" (or "confidence-through-use" as Chris prefers to call it), IEC TS 61508-3-1:2016 being one outcome of that focus. In this presentation Chris examines some of the characteristics of bugs that emerge when old, well-proven code is modified, and outlines a technique employed within BlackBerry QNX to detect those bugs.

Dr Peter Niemann, CGI

A mathematician by training, Peter has over 25 years of experience as an IT consultant and project manager. Peter has a strong focus on scientific applications within the Space Sector and has been involved with the EGNOS Programme for over two decades in a variety of functions.


The EGNOS Safety of Life Satellite Based Augmentation Service has successfully provided assured positioning across Europe since 2011. This talk follows the EGNOS DO-178B level B Check Set through its 20 years of system development and operational maintenance as a case study. We explore the advances in software engineering and lessons learnt that have forced change and driven continuous improvement. We identify which organisational structures and processes have proved most valuable, and in which respects maintenance has been constrained by historical choices.

Simon Scutt, Thales

Simon is a Safety and Airworthiness Engineer on the Thales Watchkeeper programme, with over ten years of experience in System Safety and five years of experience of Airworthiness. His background is development of real-time and safety-critical software, including the Eurofighter Typhoon, Airbus A380 and ESA Galileo programmes. 


The Watchkeeper WK450 is an Unmanned Aerial System (UAS) that provides Intelligence, Surveillance, Target Acquisition, and Reconnaissance (ISTAR) capability to the British Army. Since the programme’s inception in 2007 the Military Aviation Authority (MAA) has been established as the regulatory authority responsible for Air Safety within UK Defence. This talk discusses how the Watchkeeper programme manages software change for a legacy system under a more recent regulatory framework.


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