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Cascade model of software development

Updated at: 24 January 2025

The cascade development model (or Waterfall) is one of the earliest and simplest approaches to the software development life cycle. Its essence is that the development process is divided into several stages, each of which follows strictly one after another, without returning to the previous stages.

In other words, development proceeds as if by "cascade" or "waterfall" from top to bottom, from one stage to another:

The basic principles of the model are

    ¨NBSP;

  1. Transition from one stage of development to another occurs only after the previous stage is fully and successfully completed. For example, you cannot start writing code without having a fully approved project in hand.
  2. Or start testing if not all modules have been implemented yet;

  3. Strict project documentation. Each stage of development is described in detail in the project documentation.
  4. The cascade model is inherent in strict adherence to the outlined plan;

  5. Strict sequence of stages.
  6. The cascade model prohibits skipping stages or returning to previous stages;

  7. Any changes must be agreed with the customer and documented;

  8. Testing and error detection occurs only after the end of development;

  9. After the TOR approval, the customer does not participate in the product
  10. development
  11. process.

Stages of the cascade model of software development

The classic software development model involves the following stages:

  1. Planning (Planning)At this stage, a detailed project plan is developed. Timeline, budget, resources and tasks are defined.
  2. This stage includes defining the development team, assigning responsibilities, and creating a schedule.

  3. Requirements AnalysisThis stage involves gathering and documenting requirements for the software product. It involves communicating with the customer and end users to understand their needs.
  4. The result of this phase is the creation of a requirements document.

  5. Design (Design)This phase involves developing the architecture of the software product. The data structure, user interfaces, system components, and algorithms are designed.
  6. This stage also includes creating the user interface (UI) design and defining technical specifications.

  7. DevelopmentAt this point, active code creation begins
  8. .
  9. Developers write the program according to the requirements and design defined in the previous stages.
  10. Development may include creation of various modules, components and functional parts of the program.

  11. Testing & DeploymentDuring this stage the quality of the software product is tested using various types of testing, including unit, integration, functional and other types of testing. After testing, the software is released into production.
  12. It is installed on the target server or distributed to end users.

  13. SupportAfter release, the software continues to be maintained and updated. This stage may include implementing updates, fixing bugs, providing technical support to users, and responding to requests for changes or adding needed features.
## Advantages and disadvantages of the cascade model
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**Ease of project management.**

The cascade model provides a clear and easily manageable development process. Phases are executed sequentially, making it easy to control the project lifecycle;

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Transparency. The entire development process is presented in clear phases, making the project transparent to both developers and customers;

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Fixed requirements. Project requirements are clearly defined at the initial stage, which prevents changes during the development process;

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Project documentation. Detailed documentation is created at each phase of development, which is convenient for subsequent maintenance and support of the software product.

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Complexity of making changes. Due to its linear structure, the cascade model can be ineffective when it is necessary to respond quickly to changes in requirements after development has begun;

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Long development cycle. Since each phase is executed sequentially, the process can be long and the customer may not see the results until the entire project is completed;

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Limited interaction with the customer. The customer can only see the results after the project is complete, reducing the opportunity for real-time feedback and adjustments.

When to use the cascade model

The cascading development model is gradually losing its popularity, giving way to more flexible iterative models. Despite this, the classic "waterfall" approach is still in demand in some scenarios.

The cascade model finds its application when the customer has a clear vision of the result and wants to avoid significant changes in the development process, and does not seek to actively interact with the development team. In addition, the cascade model is suitable for projects where clear deadlines and final results of each stage are defined in advance.
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## Differences from other development models

In addition to cascading, there are several alternative software development models:

    ¨NBSP;

  • Agile Model (AgileDevelopment Methodology)Agile is based on iterative and incremental approaches with an emphasis on continuous close interaction with the customer, readiness for change, and frequent delivery of working software.
  • The model assumes flexible planning and the ability to respond quickly to changing requirements.

  • Spiral
  • Model
  • Provides for phased development with mandatory risk analysis at each iteration and the ability to return to previous stages.
  • It is distinguished by support for iterative approach and focus on risk assessment.

  • V-ModelStrict sequence of stages as in waterfall, but with emphasis on their verification and testing for compliance with the output data of the previous stage.
  • A more formalized approach than the cascade model.

  • RAD (Rapid Application Development)The basis is to reduce development time through the use of prototypes and intensive customer involvement. The model focuses on rapid creation of working versions of software.

Differences of the cascading model:

  1. Linear ApproachThe cascade model applies a linear and sequential development method where each stage is tightly dependent on the previous stage.
  2. This structured sequential execution of phases distinguishes it from other models.

  3. Limited flexibilityUnlike other models, the cascade model does not provide flexibility to respond to changes in requirements during the development process.

  4. Clear structureOne of the advantages of the cascading model is its clear structure, which makes it easy to manage the project, especially in cases where requirements are clearly defined in advance.

  5. Outcome-orientedUnlike iterative models, which focus on incremental improvement, the cascading model focuses on the complete completion of each stage before moving on to the next.