Forbid an incompatible combination

Intent

I want to detect incompatibility of two qualifications without a hidden derivation of negation.

Correct formFrozen execution sceneBoundary

Wrong form and why it stays silent

Incorrect form

// require not adult(p) считают производителем not adult(p).

A constraint reads supports four-valued, but does not add them. A constraint violation is a check finding, not a legal violation of a position.

Correct form

Arxo Law

language "law.core" version "0.2";
package recipes.g.r05 version "0.1.0";
namespace "urn:recipe:g-concepts:05";

entity Person;
relation eligible(p: Person) kind institutional;
relation young(p: Person) kind empirical;
relation adult(p: Person);
constraint Exclusive(p: Person) { when young(p); require not adult(p); severity error; }

Frozen execution scene

Facts on 13.09.2026	Question	Answer
combination presented	truth(adult(entity_ref("urn:recipe:g-concepts:05:p")))	truth_status == TRUE_ONLY; issue(CONSTRAINT_VIOLATED); / NON_EXECUTABLE
second status unknown	truth(adult(entity_ref("urn:recipe:g-concepts:05:p")))	truth_status == NEITHER; / COMPUTED
exclusion proved	truth(adult(entity_ref("urn:recipe:g-concepts:05:p")))	truth_status == FALSE_ONLY; / COMPUTED
without the constraint	truth(adult(entity_ref("urn:recipe:g-concepts:05:p")))	truth_status == TRUE_ONLY; not issue(CONSTRAINT_VIOLATED); / COMPUTED

presented combination violates constraint

Arxo Law

test "presented combination violates constraint" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00+05:00;
            knowledge_time @2026-09-13T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        assert young(entity_ref("urn:recipe:g-concepts:05:p")); assert adult(entity_ref("urn:recipe:g-concepts:05:p"));
    }
    evaluate truth(adult(entity_ref("urn:recipe:g-concepts:05:p")));
    expect truth_status == TRUE_ONLY; expect issue(CONSTRAINT_VIOLATED);
    expect evaluation_status == NON_EXECUTABLE;
}

unknown second status stays open

Arxo Law

test "unknown second status stays open" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00+05:00;
            knowledge_time @2026-09-13T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        assert young(entity_ref("urn:recipe:g-concepts:05:p"));
    }
    evaluate truth(adult(entity_ref("urn:recipe:g-concepts:05:p")));
    expect truth_status == NEITHER;
    expect evaluation_status == COMPUTED;
}

proven exception refutes

Arxo Law

test "proven exception refutes" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00+05:00;
            knowledge_time @2026-09-13T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        assert young(entity_ref("urn:recipe:g-concepts:05:p")); assert not adult(entity_ref("urn:recipe:g-concepts:05:p"));
    }
    evaluate truth(adult(entity_ref("urn:recipe:g-concepts:05:p")));
    expect truth_status == FALSE_ONLY;
    expect evaluation_status == COMPUTED;
}

removed constraint restores truth

Arxo Law

test "removed constraint restores truth" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00+05:00;
            knowledge_time @2026-09-13T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        assert young(entity_ref("urn:recipe:g-concepts:05:p")); assert adult(entity_ref("urn:recipe:g-concepts:05:p"));
    }
    evaluate truth(adult(entity_ref("urn:recipe:g-concepts:05:p")));
    expect truth_status == TRUE_ONLY; expect not issue(CONSTRAINT_VIOLATED);
    expect evaluation_status == COMPUTED;
}

Constraint verdicts are read from separate CONSTRAINT results and checked together with constraint_check nodes.

Python

>>> import runpy
>>> check = runpy.run_path("docs/recipes/g-concepts/resources/check.py")
>>> check["check_constraints"](https://github.com/arxohq/law/blob/master/docs/recipes/g-concepts/5)
'Г5: вердикты ограничений проверены; lawc = lawref'

Counterfactual

Mutation require not adult(p); → then not adult(p);: LDC-E0201.

Boundary

An issue with error severity forbids a COMPUTED document: CONSTRAINT_VIOLATED and KEY_CONFLICT make the whole document NON_EXECUTABLE. This does not erase the fact’s truth status and does not change the constraint verdict.

A rule of negative qualification is written separately. Even a VIOLATED constraint does not automatically create a sanction or a negative fact.