Stef Joosten builds register systems for government organisations that want to leave their spreadsheets behind. on Stef Joosten

Nobody oversees our spreadsheets any more

Mon, 01 Jan 0001 00:00:00 +0000

Whoever keeps a spreadsheet has thought about their reality. That knowledge is my starting point. From the data that already exists, I capture the concepts, the relations and the rules in a schema, and the register system comes from that schema.

The course of an assignment is described under the approach.

We process every change in the law by hand

Mon, 01 Jan 0001 00:00:00 +0000

In a spreadsheet, a rule lives in the head of whoever maintains it. In a register system, it lives in the schema, as a rule about the data. An entry that conflicts with that rule is made visible by the system at once. When the law changes, the rule in the schema changes, and the system points out the data that no longer comply.

The course of an assignment is described under the approach.

We want a register that guards its own rules

Mon, 01 Jan 0001 00:00:00 +0000

The schema of the register names the concepts, their relations and the rules that must always hold. The register system itself comes from that schema. So the register guards the rules that are in the schema, and no others.

The course of an assignment is described under the approach.

Why a spreadsheet is not a register

Thu, 22 Oct 2026 00:00:00 +0200

This is a trial piece, so that the build street of this site has something to test. The text follows.

About Stef

Mon, 01 Jan 0001 00:00:00 +0000

I am Stef Joosten. I work as an architect on register systems for government and co-design Ampersand, a language in which rules about data are laid down with mathematical precision.

This page will get a photo, a short overview of my work, and the systems I may name with the consent of their owners.

Approach

Mon, 01 Jan 0001 00:00:00 +0000

An assignment starts with the data that already exists. Whoever keeps a spreadsheet has thought about their reality; that knowledge is the starting point, not a model designed in isolation.

From that data a schema of concepts, relations and rules emerges. The rules guard the data: an entry that conflicts with reality or with the law is made visible by the system at once. I write such schemas in Ampersand, an open language in which a rule has exactly one meaning.

Contact

Mon, 01 Jan 0001 00:00:00 +0000

A first conversation is free and without obligation. Send an e-mail to stef@stefjoosten.nl with a few sentences about what is going on in your administration.