Compsci

Not Before Time started with a question: can time be connected to information as reliably as GPS connects position to location? The mathematics to do this is decades old and already running in production systems. I soon discovered this question has been substantially answered, and the next question was a lot more subtle: how can time-linked information be rolled out to society for practical purposes, when what we are doing is introducing a new kind of certainty? The applications sound very tempting, ranging from protecting journalists and whistleblowers to sealed commercial bids, legal instruments, and proving when AI-generated content was created. But what happens when billions of people discover that the power balance inherent in information has been inverted? ...

AI is slow, and Agentic AI ↗ is even slower. I develop an MCP server ↗ that generates PDF documents, and I work with the Agentic Perseverance Composition Engine daily. Tasks that take maybe 5 microseconds on an operating system (eg, does a file called Things-to-Do exist?) can take a million times longer – between 2 and 5 seconds – because each operation requires multiple round trips to a remote LLM, often with timeouts. It’s a young, unstable stack, comparable in maturity to early MS DOS or the Apple ][. When AI gets hold of your data via an MCP server it can do interesting things, but it is not put together well. ...

The detail of the GDPR and its implied computer science contain a solution for sharing secrets according to law. This continues to be true in 2026, as the Digital Omnibus Regulation ↗ takes shape. Executive Summary The GDPR sets up a conflict in trust between companies in particular circumstances, which can only be resolved by using the automation of a cryptographic audit trail with particular properties as described below. Problem Statement ...

When Linux was a Struggling Challenger 💡 Key Point This is a 2026 restoration of my (Dan Shearer’s) 1998-2001 guide, preserved at archive.org ↗ . Links have been updated to point to the archives where possible. In 1999 I joined my first startup, Linuxcare in San Francisco. The Linuxcare story is a quintessential United States dot-com bubble narrative, featuring a famous venture capital fund, massive growth, a failed IPO, and a fancy new ex-IBM CEO resigning under a cloud. Founded in 1998, Linuxcare aimed to be the “0800 number for Linux”. So close! ...

The Fossil ↗ source code management system is the most fully-featured alternative to Git, and has had twenty years of development and testing since 2006. After helping Fossil make some changes I now use Fossil for several projects. I also use Git extensively on various software forges (but not GitHub unless I must). Mercurial ↗ is actively maintained but has lost most of its mindshare since Mozilla ↗ , Bitbucket and others migrated away, and is rarely chosen for new projects today. ...

LumoSQL ↗ protects data on mobile phones using a new data storage technology which is highly compatible with most existing devices. With LumoSQL, the device owner has ultimate right to decide who can read or change their data… and this decision continues to be enforced even after it has been copied off the phone to (for example) a bank or insurance company for processing with their in-house database software. In contrast, the situation at present is that device owners are rarely in control of the privacy of their own data, despite many laws relating to privacy. ...

I have an interest in non-electronic computers as an educational tool. An horologer is someone who makes mechanical clocks and watches, and horologers definitely don’t believe in electronics. That’s why I published Shearer, D. (2007). "Communication: A Request for Collaboration." Horological Journal, 149(12), p. 471., which sounds much fancier than the letter to the editor it was. Given I didn’t even know the British Horological Institute ↗ existed until a week prior it makes me very pleased. ...

Large Language Models are subject to the laws of physics in a bad way, because they use so much electricity and make so much heat. I was interested to learn about a Mr Landauer and his principle of thermodynamic reversibility, which suggests physics might also help, by greatly reducing the amount of power required by AI datacentres. That still leaves many, many AI problems including an economic bubble, but it would definitely help. ...

Not-forking ↗ is a technical tool for software development. Not-forking assists with reproducibility. Here are some simple ways of explaining what Not-forking can do: Not-forking lets you integrate non-diffable codebases, a bit like patch/sed/diff/cp/mv rolled into one. Not-forking is a machine-readable file format and tool. It answers the question: What is the minimum difference between multiple source trees, and how can this difference be applied as versions change over time? Not-forking avoids duplicating source code. When one project is within another project, and the projects are external to each other, there is often pressure to fork the inner project. Not-forking avoids that. Not-forking helps address the problem of reproducibility. By giving much better control over the input source trees, it is more likely that the output binaries are the same each time. But here is the big win: Not-forking avoids project-level forking by largely automating change management in ways that version control systems ↗ such as Fossil ↗ , Git ↗ , or GitHub ↗ cannot. The full documentation ↗ goes into much more detail than this overview. ...

Reversible execution creates computers that seem to run backwards, applying time shifting techniques with simulation/virtualisation to address software unreliability and complexity. I stand by my excited comments from way back in 2005: Reversibility is the biggest advance in debugging since source code debugging — Me, on the GDB developers list ↗ In 2026, reversibility still isn’t seen as an ubiquitous must-have for software development, but awareness is increasing. 💡 Confusingly similar names I also have an article on the totally different but similar-sounding topics of logical reversibility and thermodynamic reversibility . If you’re interested in the problems power-hungry AI datacentres present the world you might find it interesting. What is checkpoint-based reversible execution? Reversible execution is about giving the appearance of a program executing backwards in time. If you’ve not seen it before, it is just as strange and impressive as it sounds. ...