About

I’m John Hearn. I write about software, systems, mathematics, organisations, and the models we use to make sense of things.

My centre of gravity is software engineering, but I am usually more interested in the ideas around it: how people think, communicate, learn, estimate, design, test, and make trade-offs inside complex systems; how we know what we think we know; where our models help or mislead us; and what simple structures can reveal about the nature of things.

I tend to learn by rebuilding things for myself, so the writing here is a mixture of essays, worked examples, simulations, and notes. The opinions are my own, and provisional. Writing is partly how I find out what I think.

About the site

The site is generated using the Quarto publishing system.

The style is inspired by the Tufte-CSS theme, a natural extension of the work done by Edward Tufte and his collaborators who created a CSS file that allows web writers to use the same simple and elegant style employed in his published materials.

The style uses liberal margin notes as an alternative to footnotes to bring additional detail closer to the relevant text.

Tufte is best known for his analysis of PowerPoint slides used by NASA engineers leading up to the Challenger disaster. This was part of a general criticism of presentation style (PowerPoint/Keynote) slides as a tool for communication, suggesting that they tend to be used for persuasion rather than to inform. I have some sympathy for that view.