Traditional SDLC vs. RAD

A software development life cycle (SDLC), also known as an application development life cycle, is a method for designing, developing, testing, and delivering software. It is made up of a series of phases, each of which builds on the results of the previous one.

The SDLC is an essential component of any software project management process. Most of the time, the project management outcome is determined by the selected software development life cycle. Many SDLC models take a methodical approach to development, such as Traditional Software Development, while some do not, focusing instead on a fast and flexible approach.

Evolution of the SDLC

The SDLC has taken numerous shapes since the first software was created and continues to do so. This occurred primarily due to changing environmental conditions and, more recently, because of digital transformation. The most popular traditional Software Development Lifecycle models developed are Waterfall, Iterative, Spiral, and V-Shaped. All models developed during this time take a distinct approach to the application development process.

With the development of the digital workforce and agile operations, today's business demands have changed. Accordingly, the SDLC continued to evolve, emphasizing agility to decrease time-to-market by developing a minimum viable product whilst putting the client at the center of the project. Whereas the traditional SDLC model is still present, emerging models, such as rapid application development (RAD), are reshaping the design of modern businesses to incorporate agile procedures.

When talking about the traditional SDLC, we often refer to the Waterfall approach because it is considered the earliest and most widely utilized methodology. Rapid Application Development is one of the most recent models developed to address the drawbacks of the previous methodologies.

Because of the many differences between Waterfall and RAD, the most appropriate methodology may be determined by various criteria. Let us look at when companies should use each of the two software development techniques.

Traditional SDLC – Waterfall

In the software development life cycle, the Waterfall model is used to design a system linearly and sequentially. This model is known as Waterfall because it advances in a systematic downward manner from one phase to the next. The output of one step is used as the input for the following one.

One of the model's key features is that each phase must be completed before the next one can begin, and the phases must not overlap. The sequential phases of the Waterfall model are:

1. Requirement Gathering and Analysis
2. System Design
3. Implementation
4. Integration and Testing
5. System Deployment
6. Maintenance

As previously mentioned, phases do not overlap in the Waterfall model, which often leads to inflexibility, which can cause issues with the software development process because it does not offer feedback between the development phases.  The requirements are fixed in stone from the start. No newly found knowledge can be used to improve the requirement once the analysis has been completed.

Similarly, once the design is complete, the analysis cannot be modified without significant consequences. Technology advances, requirements alter, and the individuals who previously approved the criteria have often moved on to better employment by the time a project is completed.

The Waterfall model is suitable for the following situations:

• Requirements are well-documented and well-defined.
• The definition of the product is consistent.
• Technology is well-understood and unchanging.
• There are no unclear criteria.
• The product is supported by many resources with the necessary knowledge.
• The project is not long.
• The speed of project delivery is not a priority.
• The client does not want to be included in the development process but wants to be informed at the start and given a working product at the conclusion.

Rapid Application Development

Rapid application development (RAD), also known as rapid application building (RAB), is a general term for adaptive software development approaches.

RAD, in contrast to the previously mentioned Waterfall, emphasizes the use of software and user input. RAD represents a radical shift in software development and in how software is designed, built, and delivered. In a traditional SDLC, the finished product might take months – if not years – to reach the consumer, which is in today’s market often unacceptable. On the other hand, in rapid application development, the product is continually demonstrated to the user to provide the required input to help enhance it.

Generally, RAD is suited for developing software that is driven by user interface requirements. It is an agile project management strategy whose main advantage is fast project turnaround, making it an attractive choice for developers who prefer fast-paced environments.

Apart from a shorter time-to-market, one of the most significant advantages of RAD is client involvement.

RAD emphasizes incremental and iterative delivery of functioning models to the client instead of following a rigid process model like the traditional SDLC. Consequently, the client receives a quick response and is involved throughout the development process. Unlike traditional methodologies, a rapid prototype allows the end-user to use the application and give feedback, rather than attempting to provide an abstract evaluation of an application the user never tried testing.

Some of the key benefits of rapid application development are:

• Better quality. High-level collaboration is why software can be more usable and more focused on business problems significant to end-users.
• Quick iterations that speed up delivery.
• Increased reusability of components.
• More projects completed on time and within budget. By developing incremental units, the chances for more significant failures are reduced to a minimum.
• Flexibility. With rapid application development, developers can more easily make the required adjustments during the development phase.

Like every other SDLC, Rapid Application Development is beneficial only in certain situations. Some of them are:

• When a system needs to be built in a short amount of time (e.g., 2-3 months).
• When the specifications are known.
• When the client wants to be involved throughout the whole life cycle.
• When it is necessary to build a system that can be modularized in a short amount of time (e.g., 2-3 months).
• When the budget allows for the hiring of modelers and the purchase of automated code generation technologies.

Following the above-mentioned situations, the RAD model is not suitable in the following cases:

• The client does not want to be included in the development process.
• Lack of technically strong team members for business requirements identification and highly-skilled developers.
• The existing system is not scalable.
• The project is large and unique – the RAD model is based on prebuilt components. In the case of a unique project, there is the possibility that these components will not be able to be used, which is why the time-to-market will not be accelerated.

What to choose

It is imperative to select the appropriate model for building a software product or application because the entire product development and testing activities are carried out based on the model.

The first notion you should keep in mind is that each method is suited for different projects, requirements, and settings. For example, choose Waterfall if you manage a simple and easy project with needs that do not have to be altered. On the other hand, if you have a project that needs to be done quickly while maintaining its quality, and there is a possibility of requirement changes during the development, choose RAD.

If we sum up all the above information in one table, we get the following: