# Narrowest Concern

> A design rule that a file is classified under the narrowest declared role that describes it accurately.

Record: `architecture:narrowest-concern`
Kind: principle
Layer: [Structural Core](https://banes-lab.com/records/layer/structural-core.md)
Severity: mandatory
Scope: file
Canonical: https://banes-lab.com/ontology#architecture-narrowest-concern

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [One Concern Per File](https://banes-lab.com/records/architecture/one-concern-per-file.md) and before [Layer Spine Precedence](https://banes-lab.com/records/architecture/layer-spine-precedence.md).

## Repair

- Refactored by: Reclassify to the Narrower Role
- Detected by: one tag carrying files of several distinct roles
- Violated by: classifying to a saturated high-level label where a narrower accurate one fits
- Measured by: files per tag, skew toward the broadest tags
- Enforced by: classification review

## Requires

- [Classification Judgment](https://banes-lab.com/records/lexicon/classification-judgment.md)

## Reinforces

- [Placement Predictability](https://banes-lab.com/records/lexicon/placement-predictability.md)

## Enables

- [Layer Spine Precedence](https://banes-lab.com/records/architecture/layer-spine-precedence.md)

## Conflicts with

- [Saturated Role Tag](https://banes-lab.com/records/lexicon/saturated-role-tag.md)

## Contracts

- [Concern Classification](https://banes-lab.com/records/algorithms/concern-classification.md)

## Severity

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

## Category

- [Taxonomy / Classification / Naming](https://banes-lab.com/records/architecture-category/taxonomy-classification-naming.md)

## Enabled by

- [One Concern Per File](https://banes-lab.com/records/architecture/one-concern-per-file.md)

## Linked from

- [The layer spine](https://banes-lab.com/software-architecture/model/the-layer-spine.md)
- [Taxonomy / Classification / Naming](https://banes-lab.com/ontology/principles/architecture-category-taxonomy-classification-naming.md)
- [Taxonomy / Classification / Naming](https://banes-lab.com/ontology/lexicon/lexicon-category-taxonomy-classification-naming.md)
- [Taxonomy](https://banes-lab.com/ontology/algorithms/algorithms-domain-taxonomy.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)