Difference between Waterfall and Spiral Models

Waterfall and Spiral models are two of the most famous and widely utilized project management models in software development. These are the process models that are utilized to create software in a well-defined, systematic, and cost-effective manner. The waterfall model is also called the classical or linear model, as it has sequential stages. In contrast, the spiral model does not have sequential stages but takes an evolutionary path. The risk in the waterfall model is higher than in the spiral model, as the errors or risks are found and fixed after each step is completed.

In this article, you will learn about the difference between Waterfall and Spiral Models. But before discussing the differences, you must know about Waterfall and Spiral Models with their advantages and disadvantages.

What is Waterfall Model?

The waterfall model is a software development process model that follows a linear sequential flow. It is a traditional paradigm for the software life cycle. As the name implies, the flow of the model is sequential, which is comparable to a waterfall in a top-down approach, which is why it is also known as the linear sequential model. It has several stages: requirement analysis, design, coding, testing, integration, implementation, and maintenance.

Although, if any phase of the model has been completed, we cannot change it, which implies that whatever is done in the earlier phase could be altered. The process flow cannot pass from bottom to top, and it always flows from top to bottom, which makes it critical to be fully preplanned to minimize the chances of product failure.

Phases of Waterfall Model

There are several phases in the waterfall model. These phases are as follows:

1. Feasibility Study

It is the first phase of SDLC. In this phase, the cost and benefits are assessed of the proposed application. The feasibility analysis must generate a document that includes the following information: issue description, technical and economic viability, alternate solutions, required resources, cost, and delivery dates.

2. Requirements gathering and analysis

It includes gathering needs from stakeholders and analyzing them to understand the project's scope and goals. It decides the project's quality in terms of ease of use, performance, functionality, portability, etc. The Software Requirement Specification (SRS) document includes a thorough statement of the issue, a likely substitute answer to the problem, a functional requirement of the software system, and limitations on the software system.

3. Design

It is a multi-step process that focuses on four aspects of a program, including interface representations, software architecture, data structure, and algorithmic details. The design phase transforms the prerequisite specification into a software representation that may be evaluated prior to the coding phase.

4. Implementation

It contains coding the software in accordance with the design necessitates. In this phase, unit testing is also utilized to check that every component of the software is functioning properly.

5. Integration and System Testing

It combines the software modules in a systematic and planned way. The integration of the components cannot be completed in a single step but rather requires several iterations. Furthermore, system testing is performed to ensure that the software system functions as stated in the SRS document. There are three phases of system testing: alpha, beta, and acceptance.

6. Deployment and Maintenance

Once the software has been tested and authorized, it is deployed to the production environment. After the software is delivered, it is analyzed for a period of time to find and resolve the errors that do not appear in the starting phases of software, which is known as maintenance.

Advantages and Disadvantages of the Waterfall Model

There are various advantages and disadvantages of the Waterfall Model. Some advantages and disadvantages of the Waterfall Model are as follows:

Advantages

1. The Waterfall model is simple to understand and use, and it is a better choice for software development projects.
2. It functions well for smaller tasks and projects with well-defined requirements.
3. It is a dependable and predictable technique for developing software.
4. It offers a clear picture of the end product's appearance and functionality.
5. It is a sequential, linear strategy that makes it simpler to estimate the time and resources needed for every project phase.

Disadvantages

1. It does not enable end-user feedback.
2. A new phase starts only after the prior phase has been finished. However, it cannot be kept in real-world projects. Phases may overlap to enhance efficiency and decrease costs.
3. It is unsuitable for complicated projects because its linear and sequential nature complicates handling numerous dependencies and interrelated components.
4. Testing is usually done toward the end of the development process in the Waterfall Model. It means that defects cannot be found until late in the development process, which may be costly and time-consuming to resolve.
5. It is a structured and sequential approach, stakeholders are usually engaged in the initial project phases (such as requirements gathering and analysis) but cannot be present in the later phases (such as implementation, testing, and deployment).

What is Spiral Model?

The spiral model is an evolutionary method of SDLC, and it is a combination of the waterfall model and the prototype model. It provides support for Risk Handling. It was first released by Barry Boehm in 1986. It can apply the iterativeness of the prototype model and controlled methodical of the linear sequential model to develop incremental versions of the software. Software releases that are made incrementally are the result of the spiral model.

It is a realistic method to develop large projects that have continuous enhancements, and it is quite an expensive model than others. The spiral model's main concept is that you must plan the aims and objectives of the project and then create the software following a spiral-like direction. The best part about this model is that you may begin a project using it and then continue working on the same model later on during the project.

Phases of Spiral Model

There are mainly four types of phases in the Spiral Model. These phases are as follows:

1. Planning

It involves determining the iteration's cost, schedule, and resources. It also entails comprehending the system's needs to maintain continuous interaction between the system analyst and the client.

2. Risk Analysis

In this phase, all potential solutions are assessed to pick the best solution. After that, the risks associated with that solution are identified, and the risks are fixed utilizing the best strategy available. At the end of this phase, the prototype is created for the ideal possible solution.

3. Engineering

It is the important phase of the spiral model that contains coding, testing, and deploying software on the client side.

4. Evaluation

Risk analysis contains estimating, identifying, and monitoring technical feasibility, such as timetable slippage and cost overrun. At the conclusion of the first iteration, after testing the build, the user evaluates the software and gives feedback. The development process moves on to the next iteration according to the customer's requirement and then utilizes a linear method to implement the user feedback. The spiral iteration method continues for the duration of the software's life.

Advantages and Disadvantages of Spiral Model

There are various advantages and disadvantages of the Spiral Model. Some advantages and disadvantages of the Spiral Model are as follows:

Advantages

1. It includes risk analysis and management at every stage, increasing security and the likelihood of avoiding assaults and breakages. The iterative development method also makes easy risk management.
2. It is suggested for large and complicated projects.
3. The Spiral Model offers an incremental and iterative approach to software development. It allows flexibility and adaptability in response to shifting requirements or unexpected events.
4. It offers regular evaluations and reviews, which may enhance the communication between the user and the development team.
5. It enables numerous iterations of the software development process, which may lead to increased software quality and reliability.

Disadvantages

1. It is costly model than others, so it is unsuitable for small projects.
2. It can be complex because it contains numerous iterations of the software development process.
3. It may be resource-intensive because it necessitates extensive preparation, risk analysis, and evaluations.
4. It may be time-consuming because it necessitates numerous assessments and reviews.
5. It is significantly more complex than other SDLC models.

Key Differences between Waterfall and Spiral Model

Here, you will learn about the key differences between Waterfall and Spiral Models. Some of the main differences between the Waterfall and Spiral Models are as follows:

1. The waterfall model is linear in nature, following a step-by-step process. In contrast, the spiral model is iterative and evolutionary, repeating the same four phases with different degrees of complexity with every iteration.
2. The waterfall model is suitable for small projects with clear objectives. In contrast, the spiral model is suitable for larger, more complicated projects.
3. The waterfall model doesn't involve any client participation. In contrast, the spiral model seeks client feedback throughout the process and provides aid to ensure that the software fulfills the client's requirements.
4. The waterfall model requires developers to collect and determine project requirements only once at the start of the process and then make their project tasks on these decisions. In contrast, the spiral model requires developers to collect requirements at the outset of each iteration.
5. As the waterfall model necessitates completing one phase before beginning the next, there is no way to return and revise work in a phase once it's complete. On the other hand, the spiral model provides for a revalidation process whenever the developers want to address an issue from an earlier iteration.
6. The waterfall model makes the single final product at the process end. On the other hand, the spiral model creates a rough functional product after every phase.
7. The waterfall model is less expensive than the spiral model. In contrast, the spiral model is more expensive than the waterfall model.

Head-to-head comparison between Waterfall and Spiral Models

Here, you will learn the head-to-head comparisons between Waterfall and Spiral Models. The main differences between Waterfall and Spiral Models are as follows:

Conclusion

Waterfall and spiral models are the two main software process models in SDLC. The spiral model differs from the waterfall model in that it includes a definite identification of the risk, which minimizes the chances of project failure. In contrast, the waterfall is risky because it has no iterations, and everything must be performed at once for a software product, which means requirements must be collected, planned, designed, coded, and integrated all at once. The waterfall model is mainly utilized for smaller projects with clear requirements. In contrast, the spiral model is mainly utilized for large and complicated projects.