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Waterfall Model

The Waterfall model is a classic approach in software development, characterized by its sequential and step-by-step methodology. It is particularly suitable for projects with clearly defined requirements and few changes during the development phase. The term 'Waterfall' is derived from the linear, downward flow of the phases, reminiscent of an actual waterfall.

The Waterfall Model in Detail

The Waterfall model is a linear approach that processes project phases in a fixed order. The different phases are separated by clear interfaces and build upon each other. Typically, the Waterfall model is divided into the following phases:

  1. Requirements Analysis
  3. System Design
  5. Implementation
  7. Integration
  9. Testing
  11. Installation
  13. Maintenance

The following sections provide a detailed explanation of these phases:

1. Requirements Analysis

In the Requirements Analysis phase, the requirements for the system to be developed are identified and documented. This includes both functional requirements, such as the desired functions and features of the system, as well as non-functional requirements, such as performance or security aspects. The result of this phase is the so-called requirements specification, which forms the basis for the subsequent phases.

2. System Design

The System Design phase deals with planning the software architecture and the structure of the system. Here, the requirements from the requirements specification are translated into a technical concept that serves as the basis for implementation. The System Design also involves decisions about the technologies, programming languages, and frameworks to be used. The result of this phase is the so-called design specification, which contains the technical specification of the system.

3. Implementation

In the Implementation phase, the components and functions of the system defined in the design specification are programmed. The software is divided into individual modules, each of which can be worked on by a developer or a team. Implementation typically follows the guidelines set in the System Design and uses the selected technologies and programming languages.

4. Integration

After the individual modules have been implemented, they are assembled into a complete system during the Integration phase. This involves defining and implementing the interfaces between the modules to ensure smooth communication and cooperation between the components. Integration ensures that the system functions as a whole and meets all requirements.

5. Testing

The Testing phase serves to verify the functionality and quality of the system. Various testing methods are applied to detect and correct possible errors or problems. These include functional tests, integration tests, and load tests. The goal of the Testing phase is to meet the requirements defined in the requirements specification and to develop a high-quality system.

6. Installation

In the Installation phase, the fully developed system is installed on the target platforms and put into operation. This includes the installation of the required software components, system configuration, and the setup of the operating environment. The installation ensures that the system functions under real conditions and can be operated.

7. Maintenance

After the system has been put into operation, the Maintenance phase begins, in which the system is continuously monitored, maintained, and adjusted. This includes fixing errors, updating software components, and implementing changes or extensions. Maintenance ensures that the system remains reliable and efficient in the long term.

Advantages and Disadvantages of the Waterfall Model

The Waterfall model offers several advantages, but also disadvantages, which should be considered when deciding for or against this approach:


  • Simple and clear structure
  • Clear separation of individual phases
  • Easily understandable and traceable
  • Suitable for projects with clearly defined requirements and few changes


  • Not very flexible with changes during the development phase
  • Testing phase starts late in the development process, which can lead to high costs for error correction
  • Lack of iterations and feedback between phases
  • Not optimal for complex and dynamic projects

Due to the mentioned advantages and disadvantages, the Waterfall model is especially suitable for projects where requirements are clearly defined from the beginning and few changes are expected during the development phase. In more complex projects or with frequent changes, agile approaches such as Scrum or Kanban are often more appropriate.