4+1 View Model

The 4+1 View Model offers a structured approach to software architecture by viewing a system from five different perspectives. These perspectives help address the needs of various stakeholders — including developers, system engineers, end-users, and project managers. By incorporating each view, the model ensures a comprehensive understanding of the system's structure, behavior, and key design decisions.

Example

To clarify how these views function together, here's a breakdown using an e-commerce platform.

Logical View

The Logical View defines the system's core functionality. Key classes include Product, implemented by PhysicalProduct and DigitalProduct, which represents different product types, and Order and Cart classes that manage the shopping and ordering process. Customer tracks user information and order history, while PaymentGateway provides a consistent interface for payment processing across different providers, like StripePayment. A UML class diagram can visually represent these relationships.

Development View

From a developer's perspective, the codebase is organized into modules such as ProductModule, OrderModule, CartModule, CustomerModule, and PaymentModule. Each module contains classes with related responsibilities, making the structure modular and allowing for easier maintenance and extension. Package diagrams can illustrate this structure.

Process View

This view focuses on the runtime behavior and interactions. When a customer places an order, OrderService orchestrates the process, working with Order to manage details, PaymentGateway to handle payment, and Customer to update the order history. Sequence diagrams can depict this flow, showing the coordination among components during key actions like order placement.

Physical View

This view shows how the application is deployed across hardware resources. The front end resides on a web server, business logic operates on an application server, and persistent data is stored on a database server. OrderRepository and ProductRepository facilitate data access, optimizing database interactions.

Scenarios

A typical scenario involves a customer selecting products, placing an order, and completing payment. OrderService handles this workflow, coordinating actions across Product, Order, and PaymentGateway, while Customer records the order history. This use case validates that the architecture cohesively supports essential business processes.