Question

Question Three

Suppose you as project manager are using the Waterfall development methodology on a large and complex project. Your manager has just read the latest article in Computerworld that advocates replacing the Waterfall methodology with Prototyping and comes to your office requesting you to switch. What will be your opinion about it?

Under what circumstances would you opt for the Prototyping model and what would be the limitations of opting it? Discuss the difference between the two methodologies, and what are the advantages and disadvantages (or limitation) of each?

Answer 1

Prototype Model Vs. Waterfall Model

The waterfall model directly delivers the final product to the user and his feedback is only taken in, before the design phase. Conversely, the prototype model creates several rough working applications and involves constant user interaction, until the developers come up with the final application, which satisfies the user.

While the waterfall model is linear, the prototype model is non linear and evolutionary in nature. Both processes have their merits and demerits. According to experts, the prototype model is well suited for online applications where user interfaces are the most important component and clients are not clear about what they exactly need in the final product.

On the other hand, the waterfall model is better suited for a more conventional software projects, where user requirements are clear, right from the start. A prototype model ensures users involvement which makes last minute changes possible. The waterfall model makes it difficult to implement any changes suggested by the user, after initial specification.

To conclude, it's apparent that prototype model is best suited when the client himself is not sure of what he wants and waterfall model is a safe bet, when the end user or client is clear about what he wants. Before deciding which model would be ideally suited for your own software development project, study the nature of the client requirements and choose a process which would give you the best chances of creating a satisfying end product.

Prototyping model:-

Prototyping is defined as the process of developing a working replication of a product or system that has to be engineered.

The Prototyping Model is one of the most popularly used Software Development Life Cycle Models (SDLC models).This model is used when the customers do not know the exact project requirements beforehand. In this model, a prototype of the end product is first developed, tested and refined as per customer feedback repeatedly till a final acceptable prototype is achieved which forms the basis for developing the final product.

In this process model, the system is partially implemented before or during the analysis phase thereby giving the customers an opportunity to see the product early in the life cycle. The process starts by interviewing the customers and developing the incomplete high-level paper model. This document is used to build the initial prototype supporting only the basic functionality as desired by the customer. Once the customer figures out the problems, the prototype is further refined to eliminate them. The process continues till the user approves the prototype and finds the working model to be satisfactory.

1. Rapid Throwaway Prototyping –
This technique offers a useful method of exploring ideas and getting customer feedback for each of them. In this method, a developed prototype need not necessarily be a part of the ultimately accepted prototype. Customer feedback helps in preventing unnecessary design faults and hence, the final prototype developed is of a better quality.

2.Evolutionary Prototyping –

In this method, the prototype developed initially is incrementally refined on the basis of customer feedback till it finally gets accepted. In comparison to Rapid Throwaway Prototyping, it offers a better approach which saves time as well as effort. This is because developing a prototype from scratch for every iteration of the process can sometimes be very frustrating for the developers.

Advantages –

• The customers get to see the partial product early in the life cycle. This ensures a greater level of customer satisfaction and comfort.
• New requirements can be easily accommodated as there is scope for refinement.
• Missing functionalities can be easily figured out.
• Errors can be detected much earlier thereby saving a lot of effort and cost, besides enhancing the quality of the software.
• The developed prototype can be reused by the developer for more complicated projects in the future.
• Flexibility in design.

Disadvantages –

• Costly w.r.t time as well as money.
• There may be too much variation in requirements each time the prototype is evaluated by the customer.
• Poor Documentation due to continuously changing customer requirements.
• It is very difficult for the developers to accommodate all the changes demanded by the customer.
• There is uncertainty in determining the number of iterations that would be required before the prototype is finally accepted by the customer.
• After seeing an early prototype, the customers sometimes demand the actual product to be delivered soon.
• Developers in a hurry to build prototypes may end up with sub-optimal solutions.
• The customer might lose interest in the product if he/she is not satisfied with the initial prototype.

Use –
The Prototyping Model should be used when the requirements of the product are not clearly understood or are unstable. It can also be used if requirements are changing quickly. This model can be successfully used for developing user interfaces, high technology software-intensive systems, and systems with complex algorithms and interfaces. It is also a very good choice to demonstrate the technical feasibility of the product.

Waterfall model:-

The Waterfall Model was the first Process Model to be introduced. It is also referred to as a linear-sequential life cycle model. It is very simple to understand and use. In a waterfall model, each phase must be completed before the next phase can begin and there is no overlapping in the phases.

Every software developed is different and requires a suitable SDLC approach to be followed based on the internal and external factors. Some situations where the use of Waterfall model is most appropriate are −

• Requirements are very well documented, clear and fixed.

• Product definition is stable.

• Technology is understood and is not dynamic.

• There are no ambiguous requirements.

• Ample resources with required expertise are available to support the product.

• The project is short.

Waterfall Model - Advantages

The advantages of waterfall development are that it allows for departmentalization and control. A schedule can be set with deadlines for each stage of development and a product can proceed through the development process model phases one by one.

Development moves from concept, through design, implementation, testing, installation, troubleshooting, and ends up at operation and maintenance. Each phase of development proceeds in strict order.

Some of the major advantages of the Waterfall Model are as follows −

• Simple and easy to understand and use

• Easy to manage due to the rigidity of the model. Each phase has specific deliverables and a review process.

• Phases are processed and completed one at a time.

• Works well for smaller projects where requirements are very well understood.

• Clearly defined stages.

• Well understood milestones.

• Easy to arrange tasks.

• Process and results are well documented.

Waterfall Model - Disadvantages

The disadvantage of waterfall development is that it does not allow much reflection or revision. Once an application is in the testing stage, it is very difficult to go back and change something that was not well-documented or thought upon in the concept stage.

The major disadvantages of the Waterfall Model are as follows −

• No working software is produced until late during the life cycle.

• High amounts of risk and uncertainty.

• Not a good model for complex and object-oriented projects.

• Poor model for long and ongoing projects.

• Not suitable for the projects where requirements are at a moderate to high risk of changing. So, risk and uncertainty is high with this process model.

• It is difficult to measure progress within stages.

• Cannot accommodate changing requirements.

• Adjusting scope during the life cycle can end a project.

• Integration is done as a "big-bang. at the very end, which doesn't allow identifying any technological or business bottleneck or challenges early.