Declare relation functionality

Intent

I want to detect two values of one key while keeping both facts.

Correct formFrozen execution sceneBoundary

Wrong form and why it stays silent

Incorrect form

// При двух адресах ключ выбирает последний; при отсутствии адреса доказывает отрицание.

KEY_CONFLICT reports two incompatible projections without deleting either. A key does not give completeness and does not prove that a row exists.

Correct form

Arxo Law

language "law.core" version "0.2";
package recipes.g.r11 version "0.1.0";
namespace "urn:recipe:g-concepts:11";

entity Person;
relation address(p: Person, city: Text) kind empirical { key(p); }
relation eligible(p: Person);
rule Registered strict { for p: Person; for city: Text; when address(p, city); then eligible(p); }

Frozen execution scene

Facts on 13.09.2026	Question	Answer
first value kept	truth(address(entity_ref("urn:recipe:g-concepts:11:p"), "A"))	truth_status == TRUE_ONLY; issue(KEY_CONFLICT); / NON_EXECUTABLE
second value kept	truth(address(entity_ref("urn:recipe:g-concepts:11:p"), "B"))	truth_status == TRUE_ONLY; issue(KEY_CONFLICT); / NON_EXECUTABLE
address unknown	truth(address(entity_ref("urn:recipe:g-concepts:11:p"), "A"))	truth_status == NEITHER; / COMPUTED
key removed	truth(address(entity_ref("urn:recipe:g-concepts:11:p"), "A"))	truth_status == TRUE_ONLY; not issue(KEY_CONFLICT); / COMPUTED

first value kept under conflict

Arxo Law

test "first value kept under conflict" {
    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 address(entity_ref("urn:recipe:g-concepts:11:p"), "A"); assert address(entity_ref("urn:recipe:g-concepts:11:p"), "B");
    }
    evaluate truth(address(entity_ref("urn:recipe:g-concepts:11:p"), "A"));
    expect truth_status == TRUE_ONLY; expect issue(KEY_CONFLICT);
    expect evaluation_status == NON_EXECUTABLE;
}

second value kept under conflict

Arxo Law

test "second value kept under conflict" {
    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 address(entity_ref("urn:recipe:g-concepts:11:p"), "A"); assert address(entity_ref("urn:recipe:g-concepts:11:p"), "B");
    }
    evaluate truth(address(entity_ref("urn:recipe:g-concepts:11:p"), "B"));
    expect truth_status == TRUE_ONLY; expect issue(KEY_CONFLICT);
    expect evaluation_status == NON_EXECUTABLE;
}

unknown address stays unknown

Arxo Law

test "unknown address stays unknown" {
    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";
        }

    }
    evaluate truth(address(entity_ref("urn:recipe:g-concepts:11:p"), "A"));
    expect truth_status == NEITHER;
    expect evaluation_status == COMPUTED;
}

removed key restores truth

Arxo Law

test "removed key 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 address(entity_ref("urn:recipe:g-concepts:11:p"), "A"); assert address(entity_ref("urn:recipe:g-concepts:11:p"), "B");
    }
    evaluate truth(address(entity_ref("urn:recipe:g-concepts:11:p"), "A"));
    expect truth_status == TRUE_ONLY; expect not issue(KEY_CONFLICT);
    expect evaluation_status == COMPUTED;
}

Counterfactual

Mutation key(p); → key(missing);: LDC-E1304.

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.

Choosing a single value requires only and cardinality handling. Two positive tuples do not make each atom BOTH: this is a data conflict, not negative support.