Iterative Waterfall Model & Spiral Model in Software Engineering

Iterative Waterfall Model


The traditional waterfall methodology is difficult to apply in a real-world software development project. As a result, the Iterative waterfall model can be regarded of as including the essential modifications to the classical waterfall model in order to make it effective in real-world software development projects. It’s basically identical to the traditional waterfall approach, with a few tweaks to improve software development productivity.

The fundamental distinction between the iterative waterfall model and the classical waterfall model is that the iterative waterfall model provides feedback pathways from each step to the phases before it. The iterative waterfall model’s feedback pathways are depicted in the diagram below.

Iterative Waterfall Model

When faults are discovered at a later stage, these feedback pathways allow programmers to remedy errors made earlier in the process. The feedback channels allow the phase in which errors are committed to be modified, and the modifications are reflected in subsequent phases. However, there is no feedback path to the stage – feasibility study, because once a project is started, it is difficult to abandon it.

It is preferable to discover errors while they are still being committed. It cuts down on the time and effort required to fix errors.

Phase Confinement of Errors:

Phase containment of errors is the notion of discovering errors as close to their places of commitment as possible.

Advantages of Iterative Waterfall Model:

  • Feedback Path –

Because there are no feedback channels in the standard waterfall paradigm, there is no mechanism for error correction. However, in the iterative waterfall approach, the feedback channel from one phase to the previous phase allows for the correction of errors, and these changes are mirrored in subsequent phases.

  • Easy to understand and use –

The iterative waterfall paradigm is simple to comprehend and apply. As a result, it’s one of the most popular software development models.

  • Cost-Effective —

Changing the strategy or requirements in the model is extremely cost-effective. Furthermore, it is ideally suited for dynamic businesses.

  • Well-organized —

With this model, less time is spent documenting, allowing the team to focus on development and design.

Drawbacks of Iterative Waterfall Model:

  • Change requests are difficult to incorporate –

A key disadvantage of the iterative waterfall model is that all needs must be explicitly documented before the development phase can begin. Customers may modify their requirements over time, but the iterative waterfall methodology does not allow for modification requests submitted after the development phase has begun.

  • Incremental delivery is not supported –

The full software is produced and tested before being delivered to the client in the iterative waterfall style. There isn’t any room for a middle delivery. As a result, clients must wait a lengthy time to receive the software.

  • Phase overlap is not supported —

The iterative waterfall paradigm presupposes that one phase can begin following the completion of the previous phase, however in real projects, phases may overlap to save time and effort.

  • Risk management is not supported –

Projects may face a variety of dangers. The Iterative Waterfall Model, on the other side, lacks a risk management mechanism.

  • Limited customer interactions –
    Customer involvement occurs at the beginning of the project, during requirement collecting, and at the end of the project, during software delivery. Because the final generated software may differ from the customers’ actual requirements, these fewer encounters with consumers may cause a slew of issues.

Software Engineering |Spiral Model


The spiral model is one of the most prominent Software Development Life Cycle models for risk management. It resembles a spiral with several loops in diagrammatic depiction. The spiral’s exact number of loops is unclear, and it varies from project to project. A Phase of the software development process is defined as each loop of the spiral. Depending on the project risks, the project manager might change the number of phases required to build the product. The project manager plays an essential role in developing a product utilizing the spiral model since the number of phases is dynamically determined by the project manager.

The spiral’s radius at any given moment symbolizes the project’s expenses (cost), while the angular dimension shows the current phase’s progress.

Spinal model


As illustrated in the diagram above, each phase of the Spiral Model is divided into four quadrants. The following sections go through the functions of these four quadrants:

  1. Objective’s determination and identify alternative solutions:

At the outset of each phase, the requirements are obtained from the consumers, and the objectives are specified, elaborated, and analyzed. Then, in this quadrant, alternative solutions for the phase are given.

  1. Determine and resolve Risks:

In the second quadrant, all viable solutions are assessed in order to choose the optimal one. The risks connected with that solution are then identified, and the risks are mitigated using the best technique possible. The Prototype is made at the end of this quadrant for the finest potential solution.

  1. Develop the next version of the product:

The identified features are developed and tested in the third quadrant. The next edition of the software is available at the end of the third quadrant.

  1. Review and make plans for the following phase:

Customers evaluate the software that has been built thus far in the fourth quadrant. Finally, the planning for the following step begins.

  1. Develop the next version of the product:

The identified features are developed and tested in the third quadrant. The next edition of the software is available at the end of the third quadrant.

  1. Review and make plans for the following phase:

Customers evaluate the software that has been built thus far in the fourth quadrant. Finally, the planning for the following step begins.

Spiral Model Risk Management

Any adversity that could be pardise the effective execution of a software project is referred to as a risk. The spiral model’s most essential aspect is how it handles unforeseen hazards once the project has begun. The development of a prototype makes such risk resolutions easier. The spiral approach encourages risky copying by allowing for the creation of a prototype at each stage of software development.

The Prototyping Model also enables risk management, although hazards must be fully identified before the project’s development activity begins. However, in real life, project risk may arise after development work has begun; in this scenario, the Prototyping Model cannot be used. The product’s features are evaluated and examined in each phase of the Spiral Model, and the risks at that moment in time are identified and resolved through prototyping. As a result, this paradigm is far more adaptable than other SDLC models.

Why Spiral Model is called Meta Model?

Because it encompasses all other SDLC models, the Spiral model is referred to as a Meta-Model. The Iterative Waterfall Model, for example, is represented by a single loop spiral. The spiral model integrates the Classical Waterfall Model’s progressive technique. The spiral model employs the Prototyping Model’s risk-handling technique of developing a prototype at the start of each phase. The spiral model can also be thought of as a support for the evolutionary model, with iterations along the spiral serving as evolutionary layers upon which the entire system is created.

Advantages of Spiral Model:
Below are some advantages of the Spiral Model.

  1. Risk Handling:

For projects with a large number of unknown risks that arise as development progresses, the Spiral Model is the best development model to use because it includes risk analysis and risk management at each stage.

  1. Large-scale projects:

The Spiral Model is suitable for large and complex projects.

  1. Flexibility in Requirements:

Using this methodology, change requests in the Requirements at a later stage can be accurately integrated.

  1. Customer Satisfaction:

Customers can monitor the product’s progress early in the software development process, and as a result, they become familiar with the system by using it before the final product is completed.

Disadvantages of Spiral Model:
Below are some main disadvantages of the spiral model.

  1. Complex:

The Spiral Model is significantly more complicated than other SDLC models.

  1. Expensive:

Due to its high cost, the Spiral Model is not appropriate for minor projects.

  1. Too much reliance on Risk Analysis:

The project’s successful completion is heavily reliant on Risk Analysis. The development of a project employing this strategy will be a failure without a large number of highly experienced professionals.

  1. Difficulty in time management:

Time management is challenging since the number of stages is unknown at the outset of the project. This makes time estimation problematic.

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