DDD Context Mapping Patterns

Context mapping defines relationships between bounded contexts, making integration strategy explicit.

Pattern	Description	Use When
Partnership	Two contexts cooperate, teams coordinate closely	Contexts must succeed or fail together
Shared Kernel	Two contexts share a small common model	Teams trust each other, shared model is small and stable
Customer-Supplier	Upstream context provides services to downstream	Clear customer relationship, negotiated contracts
Conformist	Downstream conforms to upstream model	No leverage to influence upstream
Anti-Corruption Layer (ACL)	Downstream translates upstream model to its own	Protect domain model from external system’s model
Open Host Service	Upstream provides protocol for any downstream to use	Multiple consumers, stable public API
Published Language	Well-documented shared language for integration	Industry standards, interoperability matters
Separate Ways	No integration; contexts are independent	Integration cost exceeds benefit

Example (e-commerce context map):

Sales Context (Upstream) --[Open Host Service]--> Order Fulfillment Context (Downstream)
Order Fulfillment Context --[Anti-Corruption Layer]--> Legacy Warehouse System
Billing Context --[Customer-Supplier]--> Payment Gateway (External)

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