# Reusability

> The degree to which a function or module can serve a new caller without change, because it carries no context of its first one.

Record: `architecture:reusability`
Kind: quality-attribute
Layer: [Structural Core](https://banes-lab.com/records/layer/structural-core.md)
Severity: recommended
Scope: function, module, component
Canonical: https://banes-lab.com/ontology#architecture-reusability

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Composition Over Inheritance](https://banes-lab.com/records/architecture/composition-over-inheritance.md) and before [Replaceability](https://banes-lab.com/records/architecture/replaceability.md).

## Repair

- Refactored by: Parameterize, Extract Library, Remove Context Coupling
- Detected by: environment-specific logic in reusable code
- Violated by: hardcoded context, hidden assumptions
- Measured by: reuse count, dependency portability
- Enforced by: API review, dependency rules

## Requires

- [Abstraction](https://banes-lab.com/records/architecture/abstraction.md)
- [Stable Contracts](https://banes-lab.com/records/lexicon/stable-contracts.md)

## Reinforces

- [Do Not Repeat Yourself (DRY)](https://banes-lab.com/records/architecture/duplicate-code.md)
- [Composability](https://banes-lab.com/records/architecture/composability.md)

## Enables

- [Shared Libraries](https://banes-lab.com/records/lexicon/shared-libraries.md)
- [Product Lines](https://banes-lab.com/records/lexicon/product-lines.md)

## Conflicts with

- [Context-Specific Coupling](https://banes-lab.com/records/lexicon/context-specific-coupling.md)

## In tension with

- [YAGNI](https://banes-lab.com/records/lexicon/yagni.md)
- [Over-Generalization](https://banes-lab.com/records/lexicon/over-generalization.md)

## Tensions

- [Reusability / YAGNI](https://banes-lab.com/records/tension/reusability-yagni.md)
- [Reusability / Over-Generalization](https://banes-lab.com/records/tension/over-generalization-reusability.md)

## Severity

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

## Category

- [Core Modular Design](https://banes-lab.com/records/architecture-category/core-modular-design.md)

## Enabled by

- [Single Responsibility Principle](https://banes-lab.com/records/architecture/single-responsibility.md)

## Linked from

- [Tools live in the tree](https://banes-lab.com/disciplined-methodology/build/tools-live-in-the-tree.md)
- [Core Modular Design](https://banes-lab.com/ontology/principles/architecture-category-core-modular-design.md)
- [Core Modular Design](https://banes-lab.com/ontology/lexicon/lexicon-category-core-modular-design.md)
- [Core Vocabulary](https://banes-lab.com/ontology/lexicon/lexicon-category-core-vocabulary.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)