Southwind Traders is a small trading company: it buys from suppliers, sells to customers and ships their orders. Every name, product and number here is invented. The data comes from Microsoft's Northwind sample database, renamed.
One database, many worlds
Southwind is one world in a database called World. Each world keeps its own people, things and ledger, side by side with the others. Everything that happens is done by a named person, and the database itself decides who may do what: this site only asks it.
Two rules you can watch
- Two people. A sale is never edited. One person claims a correction, and another person proves it. Whoever claimed it cannot prove it.
- Nothing is deleted. A mistake is answered by a reversing entry, a storno. The old line and the new one both stay on the file, so the history can always be read back.
How To Start shows both rules at work, in five steps.
Where the rules come from
The rules are Dimitar Hrisafov's. He still keeps his Sinclair QL, the computer Sinclair launched in 1984, with its color monitor, its disk drive and its manuals. In the summer of 2026 he wrote his ledger rules as new commands for that machine, in QL68, an emulator of the QL, starting from one sentence: "you can restate a measurement, you cannot restate an agreement." The same rules now run on SQL Server 2025, in this database.
Who made it
World and its rules are the work of Dimitar Hrisafov, a retired IT manager, with a co-author's team beside him all the way: Claude Opus 5.5 by Anthropic, which built and measured every part with him, and Claude Fable 5.1, the project's Oracle, asked on the larger designs.