Understanding Software Architecture: Concepts, Classifications, and the COLA Application Architecture

Architecture is an abstract description of the entities in a system and the relationships between them, originating from building design and evolving to support collaborative, divided work.

Every system, from an aircraft to a single e‑commerce component, requires architecture to manage complexity, and a well‑structured design yields better creative outcomes than an unstructured one.

An architect’s primary value is to simplify complexity; good architecture makes the system understandable for designers, implementers and operators.

Software architecture provides a high‑level abstraction of a system’s components, their interactions, and the constraints that guide integration, ultimately controlling complexity rather than prescribing a specific layering or methodology.

Architecture can be classified into several domains:

Business architecture – top‑level design influencing organization and technical layers.

Application architecture – defines layers, interfaces and data‑exchange protocols to meet functional and non‑functional requirements.

Distributed system architecture – addresses load balancing, service discovery, messaging, caching and distributed databases, balancing CAP trade‑offs.

Data architecture – standardises data definitions, governance and big‑data processing platforms.

Physical architecture – maps software components onto hardware, networks and servers.

Operations architecture – plans, selects and deploys operational systems.

Typical architectural styles include:

Layered architecture – separates responsibilities into distinct layers (presentation, business, data, etc.).

CQRS (Command‑Query Responsibility Segregation) – separates commands that change state from queries that read state.

Hexagonal (port‑adapter) architecture – isolates core business logic from external drivers and infrastructure.

Onion architecture – adds multiple domain‑driven layers (application, domain service, domain model, infrastructure) while keeping outer layers dependent on inner ones.

The COLA (Clean‑Object‑Layer‑Architecture) framework, open‑sourced by Alibaba, builds on these ideas. It adopts a refined three‑layer design (presentation, application, domain, infrastructure) and introduces extension points, business identities and a unified extension coordinate to support multi‑tenant, multi‑business customization.

COLA’s normative design defines module, package and naming conventions, and its overall structure follows the hexagonal and onion principles, using ports‑adapters to decouple technical details from core business logic.

The core mission of any application architecture, including COLA, is to separate core business logic from technical details, enabling easier understanding, maintenance, testing and replacement of infrastructure components.