Chris Hobbs

Abstract
As we consider their wider socio-technical aspects, the systems we are designing reveal more complexity and inter-dependencies than we had previously noticed. Bugs in a small accounting system in the UK’s Post Office Horizon system caused the deaths of at least 13 people, over 900 false convictions and imprisonments for theft, and much emotional stress.

In 2024, the Safety-Critical Systems Club established a working group of engineering and software professionals to produce guidance on the development of safe complex systems. This group has met 22 times and published a first version of its guidance in February 2025; a second version is scheduled for February 2026.

During the working group’s discussions, consideration of studies from other organisations and real-world examples, some interesting surprises have arisen that have changed the content, and even the title, of the guidance. This presentation describes some of these surprises and identifies some of the characteristics of complex systems that make traditional tools inappropriate for their analysis, raising the question of which techniques are still valid.

Biography:

Chris Hobbs was first required to make a decision about shipping some potentially dangerous software in the late 1980s, and has been interested in this topic since. He programs in Ada, C, Python, and, more recently, Rust. He particularly specialises in applying mathematical models to prove the correctness of algorithms and system design.

He is a member of the Canadian Mirror Committee considering version 3 of IEC 61508 (“Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems”) and a stakeholder in the development of UL 4600 (“Standard for Safety for the Evaluation of Autonomous Products”). He is a member of two working groups of the Safety-Critical Systems Club: one on the production of Assurance Cases and one providing guidance on the safety assurance of complex, socio-technical systems.

The third edition of his book "Embedded Software Development for Safety-Critical Systems" has just been published.

Apart from software development, Chris is a pilot and the author of "Flying Beyond: The Canadian Commercial Pilot Textbook". Working with an instructor, he has also been learning the 24 songs of Schubert's Winterreise cycle for the past 24 years.

Address:Ottawa, Canada