High Cohesion

Kind: quality-attribute

Layer: Structural Core

Record: architecture:high-cohesion

Severity: mandatory

Scope: class, module, component

Canonical: Ontology

The degree to which the members of a class or module work on the same data towards the same purpose.

Listed in Architecture principles, after Do Not Repeat Yourself (DRY) and before Low Coupling.

Requires

• Single Responsibility Principle (SRP)
• Explicit Boundaries

Reinforces

• Modularity
• Encapsulation

Enables

• Testability
• Replaceability

Conflicts with

• God Object
• Utility Dump
• Shotgun Surgery

In tension with

• Over-Specialization

Tensions

• High Cohesion / Over-Specialization

Violated by

• Divergent Change

Refactored by

• Extract Class
• Split Module
• Move Behavior to Its Owner

Severity

• mandatory

Category

• Core Modular Design

Linked from

• Node design
• A system is a graph
• Principles are typed
• The structural domain
• Anti-patterns
• Domain Architecture
• Correctness / Determinism / Verification
• Core Modular Design
• Core Modular Design
• Severity levels
• The resolutions