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Waterfall model

Introduction

Waterfall model remains one of the oldest strategies ever applied, in the development of a software. It is also known as classic life cycle model, which divides the entire software development process into five main phases. Following is the diagrammatical representation of waterfall model,

The waterfall model was proposed with feedback loops. However, most of the organizations avoid these loops. Thus this model is also called Linear Sequential Model.Staircase-style Waterfall model diagram showing five phases of software development: Communication or Requirements phase, Planning, Modeling, Construction, and Deployment. Each phase is represented in a color-coded box and connected with arrows forming a stepwise flow

1. Communication or requirements phase

In the first phase, the customer requirements are retrieved to generate customer requirements specification. Hence, all the stakeholders (or the end users) are called and their vision about the end product is enquired/collected and documented.

There are two important facts about this phase:

  • Project initiation

  • Requirements gathering

2. Analysis or planning phase

In this phase, the entire project strategy is devised. The main addressable issues in this phase are as follows:

  • The entire project schedule is estimated.

  • A thorough analysis of resource requirements is made.

  • Number of people involved in the project is determined.

  • Duration and expected cost of the project are estimated

Therefore, the main focus of this phase remains on:

  • Estimation

  • Scheduling

  • Tracking

3. Modeling phase

In this phase, the entire project scenario which was analyzed in the second phase is modelled diagrammatically. To do so, the UML diagrams are used. Modeling remains important for successful completion of the project.

The two important aspects of this phase are:

  • Analysis

  • Design

4. Construction phase

This is usually the coding phase of the software. Here, each component of the software is coded and is suitably integrated. Once the coding part is completed, the entire software is thoroughly tested.

Hence, the two most important activities performed during this phase are:

  • Coding

  • Testing

5. Deployment phase

This is the final phase in which the software is usually delivered to the end users for its effective implementation. Later, feedback is collected from the users. If the software fails to meet the users requirements, it is modified.

Hence, the important activities involved in this phase are:

  • Perfect delivery

  • Support

  • Feedbacks

Limitations of the model

Though the above software development process looked quite straight forward, it is now rarely used. Even the organizations, which remained loyal to this strategy, started raising serious objections, which added to its failure.

Advantages

  1. Simple and Easy to Understand: The Waterfall model is straightforward, making it easy to understand and implement, especially for smaller projects or teams without complex requirements.

  2. Clear Structure and Documentation: Since each phase is well-defined, it’s easier to document and track progress. This helps with maintaining clear requirements and specifications throughout the project lifecycle.

  3. Early Planning: The project scope and requirements are clearly defined at the beginning, which can help prevent scope creep and give stakeholders clear expectations about timelines and costs.

  4. Easy to Manage: Due to its linear structure, the Waterfall model is relatively simple to manage, particularly for projects where requirements are well understood upfront.

  5. Well-Suited for Small Projects: For smaller projects with fixed requirements and minimal changes, Waterfall is a good fit because it minimizes the need for iteration.

Disadvantages

  1. Inflexible to Changes: Once a phase is completed, going back and making changes can be difficult and costly. The model assumes all requirements can be fully defined at the beginning, which doesn’t always align with real-world scenarios where needs evolve.

  2. Late Testing: Testing only happens after the implementation phase, which can lead to discovering critical issues late in the development process. This increases the risk of rework and delays.

  3. Assumes All Requirements are Known: Waterfall works best when requirements are fully known from the start. However, in many projects, requirements evolve or are unclear at the outset, which can make it hard to apply the Waterfall model effectively.

  4. Limited Customer Involvement: Since the Waterfall model focuses on completing each phase before moving to the next, there is limited customer feedback during development. This means any misalignment with customer needs might not be identified until the later stages.

  5. Not Ideal for Complex Projects: For large, complex, or high-risk projects, Waterfall can be too rigid and inefficient, as it doesn’t allow for flexibility and iterative learning that might be needed to handle complex requirements.