Working notes
Articles
The object models behind Swedish registry data, the identifiers that are not keys, and the traps that only surface once the data is in production.
Swedish registry API: one key for people, property and companies
Sweden's registers are public, but access to them is not uniform. What a unified API replaces, what it does not, and how a request actually looks.
Swedish property data: fastighet, byggnad and belägenhetsadress
How the Swedish property register is actually structured — designations, parcels, buildings, addresses, coordinates — and how to walk it over HTTP.
Organisationsnummer: format, checksum and company lookup
The 10- and 12-digit forms, what the first digit means, a Luhn check you can paste, and the one-company-many-workplaces trap.