Software Architecture: Layered Model / Layers

This article is a definition of terms for the layered model – including exam questions and tags.

In a Nutshell

Layered Architecture organizes systems into separate layers with clear responsibilities – for clean separation, maintainability, and scalability.

Compact Technical Description

The layered model divides an application into vertically stacked, logically separated layers. Each layer has a responsibility and communicates only with the layer directly beneath it.

Typical:

• Presentation (UI)
• Business Logic (Controller/Services)
• Data Access (DAO/Repository)
• Infrastructure (Logging, Security, Caching)

Exam-Relevant Key Points

• Clear responsibilities per layer
• Communication only with adjacent layer
• Promotes maintainability/testability
• Frequently used in IHK projects
• Security: Validation/Access control in middle layers
• Documentation: Layer diagram + layer description

Core Components

1. UI
2. Business
3. Data Access
4. Infrastructure
5. DTOs
6. Validation
7. Error Handling
8. Service Layer
9. Auth/AuthZ
10. Build/Deploy Structure

Practical Example

Booking System:
UI (React) → Business (Java) → Data Access (JPA)

Advantages and Disadvantages

Advantages

• Good testability
• Team collaboration (Frontend/Backend/DB)
• Interchangeability

Disadvantages

• Overhead for small projects
• Performance loss with too many layers

Typical Exam Questions (with Short Answer)

1. Goal of the layered model? Separation of concerns.
2. What must a layer not do? Communicate directly with non-adjacent layers.
3. Where does validation belong? In the business layer.

Further Information

1. https://learn.microsoft.com/en-us/azure/architecture/guide/architecture-styles/layered
2. https://arc42.org/