Project Management. What is the waterfall model?

Project management always involves a specific methodology and best practices. It’s worth knowing both the modern ones and the classic ones, like waterfall.

Waterfall, or cascade model, is a linear approach in which customer requirements are gathered at the very beginning and then a coherent plan is created to implement those requirements. The cascade approach was first described by Winston W. Royce in 1970 and was quickly adopted across industries because of its logical consistency and ease of implementation. Today, this model is being displaced by modern and more flexible approaches such as Agile and Scrum.

Design principles of the waterfall model

Due to the rigidity of the model, project development is fast and the cost and deadline are predetermined. Unfortunately, this approach will give an excellent result only in projects with clear and predetermined requirements and ways to achieve them. There is no backtracking and testing is done almost after all work is completed. The cost of implementing any changes is high because you have to wait until the entire project is complete to initiate it. The general principles of the waterfall model can be stated as follows:

1. Documents and instructions are important, everything must be written.

2. The next stage of work does not start until the previous one is completed.

3. No stage can be skipped.

4. If product requirements have changed after agreement – the customer must report this formally and the task list is revised.

5. You cannot go back to a previous stage to change something.

6. No iteration – there is one common process for product development.

7. Identifying and correcting errors – only at the testing stage.

8. The customer is not involved in the product development after the list of tasks and requirements has been established.

Structure of the cascade model

The model proposed by Royce is extremely simple and understandable. According to him, work on a project should proceed in several consecutive stages, from the first to the last. Their number may vary depending on the project and the scheme – we will discuss the five-stage version:

Requirements gathering and assessment. Simply put, at this stage all the base documentation is created, according to which the work on the project will be carried out. First of all, the customer’s requirements and wishes are analyzed and then projected onto the company’s capabilities and the state of the market. The result of the analysis is a document describing what the final product should do, but not how and with what tools.

Design. At this stage the logic of product operation is established. Still no concrete implementation decisions are made, but the functioning of all product elements is described. At the end, you can already estimate how much time and personnel the project may require.

Constructing. Here we are already talking about concrete tools for the tasks. The appearance of the finished product is also developed for the first time. This stage accounts for most of the work on the project.

Testing. Quality control, beta and all other testers detect and report problems of the product. If there are a lot of bugs, it causes a return to the design stage.

Handover. The finished product can be presented to the customer and handed over. Since this stage also includes maintenance and support, interaction with the previous phases is inevitable.

Advantages of the cascade model

In recent years, waterfall has surrendered its leadership to more flexible methodologies. However, the cascade model is still relevant for large projects and organizations and has several advantages:

• resilience to staffing changes. Team members can come and go throughout the project lifecycle, but with detailed documentation, there is little or no impact on project time.
• discipline. The team is as focused and disciplined as possible to stay within the established plan. If necessary, a governing body is added to the overall model for decision making.
• flexibility in the early stages. Changes in the first three phases can be made immediately and with minimal effort. Thus, the customer and the contractor have time to radically change the concept of product operation.
• time and financial orientation. Because each phase fully delineates the outline of the future product, all team members understand their roles, work boundaries, and completion dates. This allows for a realistic and accurate assessment of the cost and time of the project.

Disadvantages of the cascade model

The waterfall model was relevant in the 1970s, but now, half a century later, more and more companies are moving away from it in favor of younger and more modern solutions. The main disadvantages of the cascade approach that discourage contractors are:

• thehuge amount of documents, requiring constant updates. Because of this, work on the project often turns into a real bureaucracy – until you agree with everyone, register everything in the documents, nothing will move forward.
• all requirements must be agreed upon right away. This is difficult because the customer himself often does not know what he wants. In such situations, flexible methodologies are more useful.
• ignoring the orderer. The lower the stage in the “cascade”, the smaller the role of the customer in it. Introducing any changes in the functionality of the product starts the whole chain of stages over again.
• late testing. This is where mistakes made at each stage are most often identified. More flexible methodologies use testing as a basic operation that occurs continuously. Waterfall lets incompetent employees handle the project – no one notices until it’s too late.

It turns out that the cascade methodology is an excellent solution in terms of time and reporting, but it is very poor in terms of quality. That’s why today it’s only recommended for three cases:

• targeting a customer requiring transparency of work and execution within the deadlines set.
• in the presence of managers with appropriate qualifications.
• when implementing a project that has no competition in the market.

Although these 3 points are becoming less common in practice, the cascade model will continue to be popular and in demand for a long time because of its transparent organization.

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