Finnish social security law is public. The systems that execute it should be too.
This project encodes section 6 of the Unemployment Security Act (Työttömyysturvalaki 1290/2002 §6) as executable logic using s(CASP). The rules determine whether a person is classified as an entrepreneur (yrittäjä) — a classification that affects unemployment benefit eligibility.
The system produces Finnish-language justification trees that explain why a decision was made. Not just the answer. The reasoning.
matti on yrittäjä, because
matti on yrityksen osaomistaja, because
ex_oy on osakeyhtiö, and
matti työskentelee johtavassa asemassa yrityksessä ex_oy, because
ex_oy on osakeyhtiö, and
matti on ex_oy:n toimitusjohtaja
matti:n tosiasiallinen omistusosuus yrityksessä ex_oy on 20%, because
matti omistaa 20% ex_oy:n osakepääomasta tai äänimäärästä
20% on vähintään 15%
Every rule traces to a specific paragraph of the statute.
s(CASP) reasons under the open-world assumption. Unstated facts are unknown, not false. This is how law works — a person not in the database is not "not an entrepreneur." Their status is unknown.
Closed-world systems (SQL, Python, conventional rule engines) get this wrong. They treat missing data as negation. s(CASP) treats it as absence of evidence, which is a fundamentally different thing.
The justification tree is not a side effect. It is the product.
docker build -t rules-as-code .Run the example query (Matti, CEO of a limited company, 20% ownership):
docker run --rm --entrypoint scasp rules-as-code \
--tree --human src/entrepreneur.pl facts/example.plRun all 18 tests:
make testAll of section 6:
- §6(1) — YEL and MYEL pension coverage as entrepreneur grounds
- §6(2) items 1-4 — Part-owner conditions with ownership thresholds (15%, 30%, 50%) for limited companies and other entities
- §6(3) — Direct and indirect ownership through intermediate entities, including equivalent control
- §6(4) — Leadership position definition (CEO, board member, equivalent) scoped to company type. Family member definition (spouse, lineal relatives in same household)
Symmetric relations (spouse, same household, lineal relative) are enforced — facts can be asserted in either direction. Family share aggregation across multiple members is handled via pre-computation at the data boundary.
| ID | Scenario | Expected |
|---|---|---|
| T01 | YEL-covered person | entrepreneur |
| T02 | MYEL-covered person | entrepreneur |
| T03 | CEO of ltd, 20% ownership | entrepreneur (item 1) |
| T04 | CEO of ltd, 10% + spouse 25% = 35% | entrepreneur (item 2) |
| T05 | Worker in ltd, 50% ownership | entrepreneur (item 3) |
| T06 | Worker in ltd, 20% + spouse 35% = 55% | entrepreneur (item 3) |
| T07 | Equivalent leadership in non-ltd, 15% | entrepreneur (item 4) |
| T08 | Equivalent leadership in non-ltd, family 30% | entrepreneur (item 4) |
| T09 | Indirect ownership via holding company | entrepreneur (item 1) |
| T09b | Equivalent control over holding company | entrepreneur |
| T10 | Worker in ltd, 14% (below 15% threshold) | not entrepreneur |
| T11 | Board member of ltd, family combined 29% (below 30%) | not entrepreneur |
| T12 | Worker in ltd, no ownership, no YEL/MYEL | not entrepreneur |
| T13 | Person holds 20% but does not work in company | not entrepreneur |
| T14 | Sibling holds 20% (not a family member under §6) | not entrepreneur |
| T15 | Lineal relative not in same household | not entrepreneur |
| T16 | CEO, spouse 12% + parent 10% = multi-member aggregation | entrepreneur (item 2) |
| T04b | Same as T04, spouse fact asserted in reverse direction | entrepreneur (symmetry) |
src/entrepreneur.pl §6 rules + Finnish #pred directives
test/t01-t16.pl Per-scenario test files
facts/example.pl Example fact base with query
Dockerfile SWI-Prolog stable + s(CASP)
Makefile build, run, query, test
Encoding law as formal logic exposes where the statute resists computation. Section 6 has 14 such points across 5 types:
| Type | Count | Example |
|---|---|---|
| Undefined term | 6 | "Equivalent control" — no computable definition in §6 |
| Aggregation gap | 2 | Family shares must be summed; s(CASP) cannot aggregate natively |
| Implicit bound | 2 | Indirect ownership depth not specified by statute |
| Symmetry assumption | 3 | Resolved — spouse/household/relative now enforce symmetry |
| Scope leak | 1 | Resolved — CEO/board scoped to limited companies |
Four were resolved in code. The rest are inherent to the statute.
The method is not specific to this statute or to Finnish law. Open-world logic, every clause traced to source, and justification in the regulated party's language apply to any rule-dense domain: clinical guidelines, tax codes, MDR/IVDR requirements, internal compliance policies.
- Työttömyysturvalaki 1290/2002 §6 — source law (Finlex)
- s(CASP) on SWI-Prolog — goal-directed answer set programming with constraints
- SWI-Prolog — host runtime
- Eepos — Kela's social security system programme
- OpenFisca — open-source rules-as-code engine for modelling tax and benefit systems
- Yle: Pian kone päättää suuresta osasta Kelan tukia — Kela's plan to automate 80% of benefit decisions using Salesforce/PwC (589M EUR)
Built by Aktagon Ltd.