Understanding Software Architecture: Concepts, Layers, and Design Principles

Architecture is both a noun describing the structural organization of a software system and a verb referring to the design and evolution process of that structure.

Key elements of architecture include:

System : the overall structure, e.g., an app's system architecture.

Module : a subdivision of the system to describe internal details.

Component : the smallest unit within a module, such as a message sender.

Relation : dependencies between modules or components.

Subsystem : a group of related modules in large‑scale systems.

Vertical (layered) architecture emphasizes separation of concerns through layers. Examples include the HAL layer in Android emulators. A typical three‑layer architecture consists of Presentation, Business Logic, and Data Access layers. A four‑layer architecture may add a Base layer for larger apps. The benefits are easier replacement, testing, and maintenance.

Horizontal (modular) architecture focuses on decoupling business modules to control complexity as the app grows. Complexity can be quantified (e.g., 4 modules → 24 possible interactions) and reduced by introducing an API service layer, lowering it to 5 interactions. Modularization enables independent development, compilation, and debugging of each module.

The article also discusses three design principles for architecture:

Fit principle : choose an architecture that matches the business type and scale.

Simplicity principle : prefer the simpler solution when both simple and complex designs satisfy requirements.

Evolution principle : start with a workable architecture and continuously refine it as the business evolves.

Cross‑platform and dynamic considerations are also covered. UI cross‑platform solutions include WebView, Weex, RN, Flutter, while C++ cross‑platform is used for performance‑critical scenarios. Dynamic solutions (WebView, Weex, mini‑programs, plugin architectures) trade off performance for flexibility.

In summary, architecture should describe the system’s organization, guide the overall methodology (layered and modular), and adhere to the three principles to adapt to business needs.