Strategic design

The goal of the most ambitious enterprise system is a tightly integrated system spanning the entire business. Yet the entire business model for almost any such organization is too large and complex to manage or even understand as a single unit. The system must be broken into smaller parts, in both concept and implementation. The challenge is to accomplish this modularity without losing the benefits of integration, allowing different parts of the system to interoperate to support the coordination of various business operations. A monolithic, all-encompassing domain model will be unwieldy and loaded with subtle duplications and contradictions. A set of small, distinct subsystems glued together with ad hoc interfaces will lack the power to solve enterprise-wide problems and allows consistency problems to arise at every integration point. The pitfalls of both extremes can be avoided with a systematic, evolving design strategy.

Even at this scale, domain-driven design does not produce models unconnected to the implementation. Every decision must have a direct impact on system development, or else it is irrelevant. Strategic design principles must guide design decisions to reduce the interdependence of parts and improve clarity without losing critical interoperability and synergy. They must focus the model to capture the conceptual core of the system, the "vision" of the system. And they must do all this without bogging the project down. To help accomplish these goals, Part IV explores three broad themes: context, distillation, and large-scale structure.

Eric Evans, "Strategic Design", in Domain-Driven Design: Tackling Complexity in the Heart of Software, 328.