# Power and valid exercise

## Intention

I want to create an effect only when a valid power is exercised.

## Incorrect form and why it stays silent

```text title="Incorrect form"
effect approve(valid(p));
```

A homemade effect name is not a materialization operation. This example needs create; the mere presence of a power does not create the effect.

## Correct form

```law
language "law.core" version "0.2";
package recipes.a.r06 version "0.1.0";
namespace "urn:recipe:a-positions:06";

entity Person;
relation registered(p: Person);
relation done(p: Person);
relation sign(p: Person);
relation competent(p: Person);
relation valid(p: Person);
rule Grant strict { for p: Person; when registered(p);
    then power Permit { holder p; exercise sign(p); valid_when competent(p); effect create(valid(p)); };
}
```

## Frozen execution scene

| Facts and snapshot | Question | Answer |
|---|---|---|
| power without exercise; 2026-09-05 | `truth(valid(entity_ref("urn:recipe:a-positions:06:p")))` | `truth_status == NEITHER;` / `COMPUTED` |
| valid exercise; 2026-09-05 | `truth(valid(entity_ref("urn:recipe:a-positions:06:p")))` | `truth_status == TRUE_ONLY;` / `COMPUTED` |
| competence not presented; 2026-09-05 | `truth(valid(entity_ref("urn:recipe:a-positions:06:p")))` | `truth_status == NEITHER;` / `COMPUTED` |

```law
test "power without exercise stays unknown" {
    given {
        context {
            legal_time @2026-09-05;
            decision_time @2026-09-05T09:00:00+05:00;
            knowledge_time @2026-09-30T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        assert registered(entity_ref("urn:recipe:a-positions:06:p")); assert competent(entity_ref("urn:recipe:a-positions:06:p"));
    }
    evaluate truth(valid(entity_ref("urn:recipe:a-positions:06:p")));
    expect truth_status == NEITHER;
    expect evaluation_status == COMPUTED;

}
```

```law
test "valid exercise establishes effect" {
    given {
        context {
            legal_time @2026-09-05;
            decision_time @2026-09-05T09:00:00+05:00;
            knowledge_time @2026-09-30T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        assert registered(entity_ref("urn:recipe:a-positions:06:p")); assert competent(entity_ref("urn:recipe:a-positions:06:p")); assert sign(entity_ref("urn:recipe:a-positions:06:p"));
    }
    evaluate truth(valid(entity_ref("urn:recipe:a-positions:06:p")));
    expect truth_status == TRUE_ONLY;
    expect evaluation_status == COMPUTED;

}
```

```law
test "missing competence blocks exercise" {
    given {
        context {
            legal_time @2026-09-05;
            decision_time @2026-09-05T09:00:00+05:00;
            knowledge_time @2026-09-30T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        assert registered(entity_ref("urn:recipe:a-positions:06:p")); assert sign(entity_ref("urn:recipe:a-positions:06:p"));
    }
    evaluate truth(valid(entity_ref("urn:recipe:a-positions:06:p")));
    expect truth_status == NEITHER;
    expect evaluation_status == COMPUTED;
    expect issue(POWER_INVALID_EXERCISE);
}
```

`effect create(valid(p))` is replaced with `effect approve(valid(p))`: check and lower are green, the effect is not created; the answer is NEITHER.

```law
test "renamed effect creates nothing" {
    given {
        context {
            legal_time @2026-09-05;
            decision_time @2026-09-05T09:00:00+05:00;
            knowledge_time @2026-09-30T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        assert registered(entity_ref("urn:recipe:a-positions:06:p")); assert competent(entity_ref("urn:recipe:a-positions:06:p")); assert sign(entity_ref("urn:recipe:a-positions:06:p"));
    }
    evaluate truth(valid(entity_ref("urn:recipe:a-positions:06:p")));
    expect truth_status == NEITHER;
    expect evaluation_status == COMPUTED;

}
```

```python
>>> import runpy
>>> check = runpy.run_path("docs/recipes/a-positions/resources/check.py")
>>> check["check_variant"](https://github.com/arxohq/law/blob/master/docs/recipes/a-positions/6)
'А6: контрфактуал подтверждён; lawc = lawref'
```

## Counterfactual

Mutation: `valid_when competent(p);` → ``; rejection LDC-E1305. Additional counterfactuals are shown as separate scenes.

## Boundary

Exercise here is represented by an established relation of accepted exercise. For presenting events with time, see [Present an event with a time](/recipes/n-package/event/). terminate/modify and unsupported operations are not substituted with create.