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Ports and Adapters

Core business logic should be isolated from external concerns (databases, UIs, external services) through ports that define required interfaces and adapters that implement them

Tension Addressed

Coupling vs. Flexibility

Recognizable As

Repository interfaces defined by domain, implemented by persistence; application core with no framework imports; testable business logic without mocking infrastructure; external dependencies wired at composition root

Canonical Sources

Cockburn, "Hexagonal Architecture" (2005); Freeman & Pryce, "Growing Object-Oriented Software, Guided by Tests" (2009)

Transfers To

Hardware Design (driver interfaces), Electronics (standardized connectors), International Trade (customs interfaces), Diplomacy (ambassadors as adapters)

Also known as hexagonal architecture or clean architecture. The key insight is that I/O is a detail - business rules should be independent of delivery mechanism.