Skip to content
Software Architecture Guide

4+1 View Model

Explanation

Section titled “Explanation”

The 4+1 View Model is a way to describe the architecture of software-intensive systems. It uses several views at the same time. Each view is written for different stakeholders. A stakeholder is anyone with an interest in the system, such as end users, developers, system engineers and project managers. (See the article Stakeholder.)

One picture cannot serve all of these readers. So the model splits the description into views.

The four views

  • Logical view. It covers the functionality the system gives to end users.
  • Development view. It shows the system from the programmer’s perspective. It concerns software management.
  • Process view. It covers the dynamic side of the system. It explains the system’s processes and how they communicate.
  • Physical view. It is also called the deployment view. It takes the system engineer’s standpoint. It maps software onto hardware.

The “+1”: scenarios

A small set of use cases, called scenarios, illustrates the architecture. These scenarios form a fifth view. (See the article Use Case.)

Link to other approaches

The C4 model was inspired by UML and by the 4+1 model. See the articles C4 Model and Unified Modeling Language (UML).

Example

Section titled “Example”

A team builds an online ticket shop. The logical view describes what customers can do: search events, pick seats, pay. The development view shows how programmers organize the code. The process view shows how the system’s processes communicate while it runs. The physical view shows which hardware runs which parts. One scenario, “a customer buys two tickets”, illustrates the architecture across these views.

Scenarios illustrate the architecture across the four views.

Diagram source 
flowchart TD
  S[Scenarios: use cases]
  L[Logical view]
  D[Development view]
  P[Process view]
  Y[Physical view]
  S --- L
  S --- D
  S --- P
  S --- Y

Checks

Section titled “Checks”
  • The architecture description uses several views, each aimed at named stakeholders.
  • The description covers the logical, development, process and physical (deployment) views.
  • A small set of scenarios or use cases illustrates the architecture as a fifth view.
Section titled “Related”

Sources

Section titled “Sources”