# Joinable Mandated Field

> A rule or precondition that a mandated field takes a value from a closed set or an identifier, or declares that it is written for readers, so a governed surface never looks measured on a property nothing can read.

Record: `architecture:joinable-mandated-field`
Kind: constraint
Layer: [Execution Core](https://banes-lab.com/records/layer/execution-core.md)
Severity: recommended
Scope: field, schema
Canonical: https://banes-lab.com/ontology#architecture-joinable-mandated-field

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Carrier and Payload Split](https://banes-lab.com/records/architecture/carrier-and-payload-split.md) and before [Single Aggregate](https://banes-lab.com/records/architecture/single-aggregate.md).

## Repair

- Refactored by: Draw the Value From a Closed Set, or Declare the Field for Readers
- Detected by: a mandated prose field that no declaration marks as written for readers
- Violated by: mandating a field as free prose while assuming a consumer will read it
- Measured by: mandated fields in neither a resolvable form nor declared for readers
- Enforced by: coordination review

## Requires

- [Carrier Field](https://banes-lab.com/records/lexicon/carrier-field.md)

## Reinforces

- [Carrier and Payload Split](https://banes-lab.com/records/architecture/carrier-and-payload-split.md)

## Enables

- [Traceable Guarantee](https://banes-lab.com/records/lexicon/traceable-guarantee.md)

## Severity

- [recommended](https://banes-lab.com/records/vocabulary/severity-recommended.md)

## Category

- [Coordination Surfaces](https://banes-lab.com/records/architecture-category/coordination-surfaces.md)

## Linked from

- [Coordination Surfaces](https://banes-lab.com/ontology/principles/architecture-category-coordination-surfaces.md)
- [Coordination Surfaces](https://banes-lab.com/ontology/lexicon/lexicon-category-coordination-surfaces.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)

## Evidence in the code

- [models/coordination.model.md](https://banes-lab.com/source/coordination/models/coordination.model.md.md)