A defeater blocks every ground of the head

Intention

I want to keep an independent ground by shielding it from a general defeater.

An independent ground survives a general defeater only with an established priority.

Correct formFrozen execution sceneBoundary

Incorrect form and why it stays silent

Incorrect form

rule Block defeater { for p: Person; when special(p); defeat allowed(p); }
// Без приоритета он блокирует и Independent.

A defeater addresses the conclusion, not the name of one rule. Priority of Independent over it preserves the independent ground.

Correct form

Arxo Law

language "law.core" version "0.2";
package recipes.b.r04 version "0.1.0";
namespace "urn:recipe:b-rules:04";

entity Person;
relation eligible(p: Person);
relation special(p: Person);
relation allowed(p: Person);
relation independent(p: Person);
rule General defeasible { for p: Person; when eligible(p); then allowed(p); }
rule Independent defeasible { for p: Person; when independent(p); then allowed(p); }
rule Block defeater { for p: Person; when special(p); defeat allowed(p); }
priority KeepIndependent { prefer Independent over Block; reason explicit_exception; }

Frozen execution scene

Facts and choice	Question	Answer
general ground lifted	truth(allowed(entity_ref("urn:recipe:b-rules:04:p")))	NEITHER / COMPUTED
independent ground shielded	truth(allowed(entity_ref("urn:recipe:b-rules:04:p")))	TRUE_ONLY / COMPUTED
shield removed	truth(allowed(entity_ref("urn:recipe:b-rules:04:p")))	NEITHER / COMPUTED

general ground defeated

Arxo Law

test "general ground defeated" {
    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 eligible(entity_ref("urn:recipe:b-rules:04:p")); assert special(entity_ref("urn:recipe:b-rules:04:p"));
    }
    evaluate truth(allowed(entity_ref("urn:recipe:b-rules:04:p")));
    expect truth_status == NEITHER;
    expect evaluation_status == COMPUTED;
}

independent ground protected

Arxo Law

test "independent ground protected" {
    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 eligible(entity_ref("urn:recipe:b-rules:04:p")); assert special(entity_ref("urn:recipe:b-rules:04:p")); assert independent(entity_ref("urn:recipe:b-rules:04:p"));
    }
    evaluate truth(allowed(entity_ref("urn:recipe:b-rules:04:p")));
    expect truth_status == TRUE_ONLY;
    expect evaluation_status == COMPUTED;
}

protection removed

Arxo Law

test "protection removed" {
    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 eligible(entity_ref("urn:recipe:b-rules:04:p")); assert special(entity_ref("urn:recipe:b-rules:04:p")); assert independent(entity_ref("urn:recipe:b-rules:04:p"));
    }
    evaluate truth(allowed(entity_ref("urn:recipe:b-rules:04:p")));
    expect truth_status == NEITHER;
    expect evaluation_status == COMPUTED;
}

Counterfactual

Mutation: defeat allowed(p); → defeat eligible(p);; rejection LDC-E4112. Scenes that delete a fragment are marked explicitly in the table.

Boundary

If the exception concerns only one ground, the grounds can be split across predicates. Priority must follow the rule, not the desired answer.

Pitfall

A defeater blocks every ground of its head: without an established priority, the independent ground does not survive.