Software Architecture

Definition

The architecture of a software system is the shape given to that system by those who build it. The form of that shape is in the division of that system into components, the arrangement of those components, and the ways in which those components communicate with each other.

leave as many options open as possible, for as long as possible
minimize lifetime cost of the system and maximize programmer productivity
support life cycle of the system ()
makes the system easy to understand, easy to develop, easy to maintain and easy to deploy
low-level components depend on high-level components (Dependency Inversion Principle)
- reduces impact of change
  - trivial but urgent changes at the lowest levels of the system have little to no impact on the higher, more important, levels
centered on so that can describe the structures supporting those use cases without committing to frameworks/tools/environments

policies
- business rules and procedures
- where the true value of the system lives
details

Richards and Ford define software architecture along four interlocking dimensions:

Architecture style — the named topology chosen as a starting point (e.g. layered, microservices, event-driven)
Architectural characteristics — the “-ilities” the system must support (scalability, availability, maintainability, …)
Logical components — the building blocks implementing the system’s behavior (domains, entities, workflows)
Architecture decisions — the rules that constrain how the system is constructed; they form the constraints and direct development teams

These three universal truths cut across all architecture work (Richards & Ford, FSA 2E):

Everything in software architecture is a trade-off. — corollary: if you think you’ve found something that isn’t a trade-off, you just haven’t identified it yet.
Why is more important than how. — decisions made in context; the rationale (including trade-offs considered) matters more than the mechanism.
Most architecture decisions aren’t binary but rather exist on a spectrum between extremes.

There are no right or wrong answers in architecture — only trade-offs.

Neal Ford