Shift the burden after a presumption

Intent

I want to change the party to whom the rule assigns proof.

Correct formFrozen execution sceneBoundary

Wrong form and why it stays silent

Incorrect form

priority Shift { prefer Release over Default; reason explicit_exception; } // само по себе не создаёт must_prove(b)

Priority resolves a clash of two conclusions about one party. The other party is assigned the burden by a standalone Transfer rule; the duty window and goal are added as in Require an issue to be established within a deadline.

Correct form

Arxo Law

language "law.core" version "0.2";
package recipes.d.r02 version "0.1.0";
namespace "urn:recipe:d-evidence:02";

entity Party;
relation dispute(a: Party, b: Party);
relation presumed(a: Party);
relation must_prove(p: Party);
rule Default defeasible { for a: Party; for b: Party; when dispute(a,b); then must_prove(a); }
rule Release defeasible { for a: Party; for b: Party; when dispute(a,b) and presumed(a); then not must_prove(a); }
rule Transfer defeasible { for a: Party; for b: Party; when dispute(a,b) and presumed(a); then must_prove(b); }
priority Shift { prefer Release over Default; reason explicit_exception; }

Frozen execution scene

In the table P and Q are different entities of the page, C is a case; full identifiers are pinned in the scenes.

Input on 13.09.2026 (a different date is named in the scene)	Question	Answer
ordinary allocation	truth(must_prove(P))	TRUE_ONLY / COMPUTED
party released	truth(must_prove(P))	FALSE_ONLY / COMPUTED
other party assigned	truth(must_prove(Q))	TRUE_ONLY / COMPUTED
without the transfer rule	truth(must_prove(Q))	NEITHER / COMPUTED

default burden on first party

Arxo Law

test "default burden on first party" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00Z;
            knowledge_time @2026-09-13T09:00:00Z;
            timezone "UTC";
        }
        assert dispute(entity_ref("urn:recipe:d-evidence:02:p"),entity_ref("urn:recipe:d-evidence:02:q"));
    }
    evaluate truth(must_prove(entity_ref("urn:recipe:d-evidence:02:p")));
    expect truth_status == TRUE_ONLY;
    expect evaluation_status == COMPUTED;

}

presumed party released from burden

Arxo Law

test "presumed party released from burden" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00Z;
            knowledge_time @2026-09-13T09:00:00Z;
            timezone "UTC";
        }
        assert dispute(entity_ref("urn:recipe:d-evidence:02:p"),entity_ref("urn:recipe:d-evidence:02:q")); assert presumed(entity_ref("urn:recipe:d-evidence:02:p"));
    }
    evaluate truth(must_prove(entity_ref("urn:recipe:d-evidence:02:p")));
    expect truth_status == FALSE_ONLY;
    expect evaluation_status == COMPUTED;

}

burden assigned to other party

Arxo Law

test "burden assigned to other party" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00Z;
            knowledge_time @2026-09-13T09:00:00Z;
            timezone "UTC";
        }
        assert dispute(entity_ref("urn:recipe:d-evidence:02:p"),entity_ref("urn:recipe:d-evidence:02:q")); assert presumed(entity_ref("urn:recipe:d-evidence:02:p"));
    }
    evaluate truth(must_prove(entity_ref("urn:recipe:d-evidence:02:q")));
    expect truth_status == TRUE_ONLY;
    expect evaluation_status == COMPUTED;

}

no transfer rule leaves neither

Arxo Law

test "no transfer rule leaves neither" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00Z;
            knowledge_time @2026-09-13T09:00:00Z;
            timezone "UTC";
        }
        assert dispute(entity_ref("urn:recipe:d-evidence:02:p"),entity_ref("urn:recipe:d-evidence:02:q")); assert presumed(entity_ref("urn:recipe:d-evidence:02:p"));
    }
    evaluate truth(must_prove(entity_ref("urn:recipe:d-evidence:02:q")));
    expect truth_status == NEITHER;
    expect evaluation_status == COMPUTED;

}

The counterfactual program differs only by the mutation named below; its scene:

missing priority keeps both conclusions

Arxo Law

test "missing priority keeps both conclusions" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00Z;
            knowledge_time @2026-09-13T09:00:00Z;
            timezone "UTC";
        }
        assert dispute(entity_ref("urn:recipe:d-evidence:02:p"),entity_ref("urn:recipe:d-evidence:02:q")); assert presumed(entity_ref("urn:recipe:d-evidence:02:p"));
    }
    evaluate truth(must_prove(entity_ref("urn:recipe:d-evidence:02:p")));
    expect truth_status == BOTH;
    expect evaluation_status == COMPUTED;

}

Python

>>> import runpy
>>> check = runpy.run_path("docs/recipes/d-evidence/resources/check.py")
>>> check["check_variant"](https://github.com/arxohq/law/blob/master/docs/recipes/d-evidence/2)
'Д2: контрфактуал подтверждён; lawc = lawref'

Counterfactual

Diagnostic mutation (check) — LDC-E4108.

Original fragment:

Arxo Law

priority Shift { prefer Release over Default; reason explicit_exception; }

Replacement:

Arxo Law

priority Shift { prefer Missing over Default; reason explicit_exception; }

The paired scenes above pin the change of outcome.

Boundary

must_prove is a local allocation, not a created duty position. Priority of two compatible duties with different bearers does not by itself extinguish one of them. The normative position is Require an issue to be established within a deadline.

The counterfactual mutation removes priority Shift { prefer Release over Default; reason explicit_exception; }: under the same facts, must_prove of the first party becomes BOTH.

Pitfall

Priority alone does not move the burden: the other party is assigned by a standalone Transfer rule.