nw-ddd-tactical

领域战术设计规则：聚合、实体、事件与反模式检查。

教你如何把领域模型拆成聚合（aggregate）、实体、值对象、领域事件和仓库，明确一致性边界和事务边界，适合在建模或实现领域逻辑时用。给出可执行的设计规则和常见反模式提示，帮你识别哪些对象必须放在同一个聚合、哪些应该分离。目标是把复杂业务拆成可维护、可验证的小单元。

# Tactical DDD

Implementation patterns within a bounded context. Tactical DDD answers: "How do we structure the domain model?"

## Aggregates

An aggregate is a consistency boundary -- a cluster of domain objects that must be transactionally consistent.

### Vernon's Four Design Rules

1. **Model true invariants in consistency boundaries**: Only include elements that MUST be consistent within the same transaction. If two entities don't share an invariant, they belong in separate aggregates.

2. **Design small aggregates**: ~70% of aggregates contain only a root entity with value-typed properties. Large aggregates create concurrency contention, scalability failures, and memory pressure.

3.