Domain Model

Translation boundary protecting a bounded context's model from upstream language corruption; structure (FACADE+ADAPTER); ACL vs Conformist vs Open-Host Service; migration use with Strangler Fig

Four-pattern spectrum: transaction script, active record, domain model, event-sourced domain model; subdomain-to-pattern mapping; transaction script failure modes; full tactical decision tree (pattern→architecture→testing strategy); migration paths between patterns

DDD tactical pattern for core subdomain business logic: value objects (immutable, identified by values), entities, aggregates (consistency boundary, one-per-transaction rule, aggregate root, OCC), domain events, domain services; Evans elaborations on associations, entity identity, context-dependent entity/VO classification, service partitioning, modules as model elements

*Domain-Driven Design* — Eric Evans

CDC, event sourcing, CQRS, immutability, write/read path, correctness without coordination; DDD: CQRS sync/async projections, architectural slices, event-sourced domain model four-step cycle; Fowler's four-way event taxonomy (notification/state-transfer/event-sourcing/CQRS)

Evans' binding principle: one model for analysis and design; code is the model's expression; hands-on modellers; bones-showing; requires layered architecture for domain isolation; breakthroughs: non-linear returns, cascade of insights, Share Pie story

O/R mapping architectural patterns (Table Data Gateway, Row Data Gateway, Active Record, Data Mapper); behavioural patterns (Unit of Work, Identity Map, Lazy Load); structural mapping; inheritance strategies (Single/Class/Concrete Table Inheritance)

Hexagonal/onion/clean architecture; DIP-inverted dependencies; business logic at centre; DDD fit: domain model and event-sourced domain model; architectural slices principle