Layers upon layers, they're everywhere I look!

Effective layer design is fundamental to Layered architecture, becoming instinctive for programmers who adhere to the principles outlined below:

  • Encapsulation: A key guideline is to focus on implementation details while accepting potential failures. Why encapsulate? For numerous reasons, including enhanced safety and security.
  • Cohesion: You're likely familiar with the Single Responsibility Principle. Cohesion reflects how strongly a layer's components are unified around its purpose. Effective glue code fosters stronger cohesion within layers.
  • Loose Coupling: Ideally, a layer should expose a single, maintainable, and reusable interface. Complex software relies on the seamless interaction of modules. By coding to an interface and leveraging polymorphism, we can support diverse object hierarchies without tightly binding the interface to a specific client type.
  • Composition: Combining composition with tight coupling enhances the cohesiveness of glue code.
  • Fence: Enforcing strict separation between layers, ensuring communication occurs only through defined interfaces.
  • Boundary: The collective set of interfaces.
  • Interface: A balance of boundary and fence. An interface is abstract enough to conceal a layer's implementation details while remaining minimal and straightforward to fulfill the layer's purpose.
  • Abstraction: As noted, abstraction serves multiple purposes. It enables changes to a layer's internal implementation or external interactions without altering the interface, allowing seamless updates while preserving functionality.