An API for Belgian healthcare nomenclature

What Belgian nomenclature is

The catalogue of reimbursable healthcare services in Belgium. Each service has a code number, an official description in Dutch and French, a place in a chapter and article structure, and one or more amounts attached to it.

It is the vocabulary Belgian healthcare billing is written in. If your software has to say what was done and what it costs, it has to speak this.

The structure

Eleven chapters, each with articles — and articles are not numbers: `27/1`, `35bis` and `28§1` are all real article identifiers, which is why this API treats them as strings rather than integers. Below articles sit sub-articles, and codes are also grouped by discipline.

History is the hard part

Codes are introduced and retired, descriptions are reworded, amounts are indexed. A system that only knows today cannot answer a question about last year, and healthcare billing asks about last year constantly.

Every versioned fact keeps its own validity window, so nothing is ever overwritten: a tariff moving from €32.84 to €33.74 is a period that ended and a period that began, both still queryable.