What Is Architecture? From 4+1 to C4 and Enterprise EA Explained

Table of Contents

1. Understanding Architecture

1.1 4+1 Model

1.2 C4 Model

1.3 TOGAF‑4A Architecture

1.4 Internet Model

2. What Is Enterprise Architecture?

What Is Architecture?

Architecture is a description of a system. Wikipedia defines software architecture as an abstract description of a software system’s overall structure and its components, used to guide design decisions for large systems.

The three key characteristics of a system that manifest in its architecture are horizontal composability, vertical derivability, and overall evolvability. Because internet‑scale software systems constantly grow in complexity, the primary goal of architecture is to control that complexity and keep the system manageable.

1.1 4+1 View Model

The 4+1 view model, proposed by Philippe Kruchten, describes software from five perspectives: logical (user‑oriented), development (code‑oriented), process (runtime behavior), physical (deployment), and scenarios (use‑case). These five views together form five architectural models that abstract the system from scenario to deployment.

1.2 C4 Model

The C4 model, created by Simon Brown between 2006 and 2011, builds on the 4+1 model and consists of four layers:

Context: Describes the system’s relationships with external systems and people.

Containers: Functional units such as services or technical components.

Components: Parts that make up each container, e.g., modules within a service.

Code: The actual code level, including classes, interfaces, and objects.

The model expands from a macro view (the whole system) down to a micro view (individual code), much like zooming in with a magnifying glass.

1.3 TOGAF‑4A Architecture

TOGAF defines four architecture domains:

Business Architecture: Strategy, governance, organization, and core business processes; focuses on value, information, and collaboration.

Application Architecture: Blueprint of applications, their interactions, and alignment with core business processes.

Data Architecture: Logical and physical structure of an organization’s data assets and management resources.

Technology Architecture: Logical software and hardware needed to support business, data, and application services, including infrastructure, middleware, networking, and standards.

TOGAF’s purpose is to help enterprises evolve from heterogeneous to homogeneous IT, from reactive to proactive planning, from fragmented to unified systems, and from disorder to order.

1.4 Internet Model

In the fast‑moving internet industry, architecture is often expressed as three layers: business architecture, technical architecture, and deployment architecture, reflecting the short lifecycle of internet products.

2. What Is Enterprise Architecture?

Enterprise Architecture (EA) addresses the complexity of coordinating dozens of systems, hundreds of processes, and thousands of employees as an organization grows. It connects people, processes, technology, and information/data to enable long‑term, informed decision‑making.

Common misunderstandings about EA include:

Confusing EA with technical architecture only.

Thinking that producing diagrams or models alone constitutes EA.

Believing EA concerns only high‑level strategy and not operational execution.

Equating EA value with the completeness of documentation or model density.

Effective EA requires asking strategic questions—where we want to go, how we get there, and what the current state is—while using models as decision‑support tools.

EA operates on three layers:

Strategic layer: Helps leadership understand the current organization and future vision.

Business layer: Models core capabilities and processes to identify bottlenecks and optimize workflows.

Technical layer: Ensures that information, data, and system designs support strategic goals without becoming obstacles.

Ultimately, EA is a systems‑thinking approach that links people, processes, technology, and data, guiding organizations from today’s state to a desired future state.