The Pragmatic Craftsman :: Simplicity from complexity ::

Constructing a good architecture is a tough task. In my developer’s career, I have not come across too many architects that really do a decent job creating good – cohesive – architectures. That just reiterates my point that architecting a system is not an easy task.

What is a good architecture, though? What are its characteristics? I found some definite answers to this question in a book I’m reading now, Object Oriented Analysis and Design with Applications, 3rd edition. These are some of the best definitions and views on software architecture I have come across.

“A system that has a sound architecture is one that has conceptual integrity. Having a “clean internal structure” is essential to constructing a system that is understandable, can be extended and reorganized, and is maintainable and testable.”

“There is no right way to craft the architecture of a given system.”

Three Common Attributes of Good Software Architectures
1. They are constructed in a well-defined layers of abstraction, each layer representing a coherent abstraction, provided through a well-defined and controlled interface, and built on equally well-defined and controlled facilities at lower levels of abstraction.
2. There is a clear separation of concerns between the interface and implementation of each layer, making it possible to change the implementation of a layer without violating the assumptions made by its clients.
3. The architecture is simple: Common behavior is achieved through common abstractions and common mechanisms.

Architectures constructed in this way tend to be less complex and more robust and resilient. They also enable more effective reuse.