# Do Not Repeat Yourself

> A design rule that each piece of logic, constant or schema has one source in the code, and every other use refers to it.

Record: `architecture:duplicate-code`
Kind: principle
Layer: [Structural Core](https://banes-lab.com/records/layer/structural-core.md)
Severity: mandatory
Scope: function, module, domain
Aliases: DRY
Canonical: https://banes-lab.com/ontology#architecture-duplicate-code

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Separation of Concerns](https://banes-lab.com/records/architecture/separation-of-concerns.md) and before [High Cohesion](https://banes-lab.com/records/architecture/high-cohesion.md).

## Repair

- Refactored by: Extract Function, Extract Module, Parameterize, Centralize Rule
- Detected by: clone detection, duplicated branches, repeated literals
- Violated by: duplicated logic, duplicated constants, duplicated schemas
- Measured by: duplication percentage, clone count
- Enforced by: clone analyzers, lint rules, review gates

## Requires

- [Abstraction](https://banes-lab.com/records/architecture/abstraction.md)
- [Canonical Source](https://banes-lab.com/records/lexicon/canonical-source.md)

## Reinforces

- [Single Source of Truth](https://banes-lab.com/records/architecture/single-source-of-truth.md)
- [Reusability](https://banes-lab.com/records/architecture/reusability.md)

## Enables

- [Consistency](https://banes-lab.com/records/architecture/consistency.md)
- [Maintainability](https://banes-lab.com/records/lexicon/maintainability.md)

## Conflicts with

- [Copy-Paste Programming](https://banes-lab.com/records/lexicon/copy-paste-programming.md)

## In tension with

- [Locality of Behavior](https://banes-lab.com/records/lexicon/locality-of-behavior.md)
- [Simplicity](https://banes-lab.com/records/lexicon/simplicity.md)

## Tensions

- [Do Not Repeat Yourself (DRY) / Locality of Behavior](https://banes-lab.com/records/tension/do-not-repeat-yourself-dry-locality-of-behavior.md)
- [Do Not Repeat Yourself (DRY) / Simplicity](https://banes-lab.com/records/tension/do-not-repeat-yourself-dry-simplicity.md)

## Severity

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

## Category

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

## Enforced by

- [rules/eslint/closure-no-platform-capability-redefine.eslint.rule.ts](https://banes-lab.com/source/governance/rules/eslint/closure-no-platform-capability-redefine.eslint.rule.ts.md)

## Reinforced by

- [Metaprogramming](https://banes-lab.com/records/architecture/metaprogramming.md)
- [Normalization](https://banes-lab.com/records/architecture/normalization.md)

## Linked from

- [One home](https://banes-lab.com/disciplined-methodology/build/one-home.md)
- [Counting copies](https://banes-lab.com/disciplined-methodology/verify/counting-copies.md)
- [The structural domain](https://banes-lab.com/software-architecture/principles/the-structural-domain.md)
- [Separate, trade, or mitigate](https://banes-lab.com/software-architecture/principles/separate-trade-or-mitigate.md)
- [The principle architecture](https://banes-lab.com/software-architecture/glossary/the-principle-architecture.md)
- [Core Modular Design](https://banes-lab.com/ontology/principles/architecture-category-core-modular-design.md)
- [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md)
- [Schema / Canonical Data / Semantics](https://banes-lab.com/ontology/principles/architecture-category-schema-canonical-data-semantics.md)
- [Transactions / State / Concurrency](https://banes-lab.com/ontology/principles/architecture-category-transactions-state-concurrency.md)
- [Core Modular Design](https://banes-lab.com/ontology/lexicon/lexicon-category-core-modular-design.md)
- [Quality Attributes](https://banes-lab.com/ontology/lexicon/lexicon-category-quality-attributes.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)