Compsci

Automatic file versioning is a very handy tool for reducing user errors and confusion, but not many people know this because only one versioning filesystem has been implemented in production. The OpenVMS ↗ operating system and its versioned filesystem was reckoned to have ten million users or more ↗ in 2004 across half a million or so VMS clusters. I was one of those users, and I have wanted versioning on my operating systems ever since. User file versioning been reinvented many times in free software but never more than short-lived experiments. In today’s world of cloud computing, AI and mobile devices this feature feels more relevant than ever. ...

In responding to a recent security problem I had to consider the idea of intent in computer software, so I looked to see what Margaret Hamilton ↗ has to say. Hamilton proved her ideas spectacularly during the first Apollo moon landing in 1969. A hardware failure generated unexpected errors ↗ , but the software coped by running the highest-priority tasks despite the barrage of errors and prevented an abort just seconds before landing on the surface. I eventually found two 1994 articles of hers in Electronic Design magazine: one explaining her Development Before the Fact philosophy , and one describing the tools built from it . After discussion with the current magazine editor, I was able to clean up the scanned text of both and document Hamilton’s prescience. ...

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. So its either Fossil or Git. ...

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. Today, 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. ...