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First proposed by IBM during the 1980s, Rapid Application Development model is one of the popular SDLC models. Also known as the RAD model, the software development model favors speed and flexibility over thorough upfront planning.
The RAD model has a very short development time span. Generally, a project being developed with the RAD approach has a delivery time of 60 to 90 days.
One of the most important highlights of the Rapid Application Development model is the support for powerful development tools, such as C++, Java, Visual Basic, and XML, and techniques it brings to the table.
The RAD Approach
Any software development project that is divisible into smaller modules, which are capable to be assigned independently to different teams can be developed using the RAD approach. All these various modules are ultimately combined to get the final product.
The development of each module of a software development project using the RAD model follows the several basic steps of the waterfall model. These include analyzing, designing, coding, testing, implementation, and maintenance.
The Rapid Application Development approach prioritizes rapid prototyping as well as quick feedback overextended development and testing cycles.
RAD developers are allowed to make numerous iterations and updates to the project under development without starting the development schedule from scratch each and every time.
The inception of RAD started when software developers started to realize that the traditional waterfall model wasn’t much effective. The waterfall model is incapable to accommodate software development projects with evolving requirements.
A major drawback of the waterfall model is that once the software development process reaches the testing phase, it almost becomes impossible to change the core functionality and features offered by the software under development.
Though the RAD model appeared during the 1980s, it has evolved ever since. This is in sharp contrast to the waterfall model, which is the same today as it was during its advent.
Phases of the RAD Model
The process of the RAD approach involves building a prototype and then delivering it to the customer to get the feedback. This feedback is then taken in and changes are made to the prototype before delivering it again to the customer.
The process repeats until validation is done by the customer. Afterwards, the SRS document is developed and the design is finalized. The end product is then built around this finalized design.
There are 4 distinct phases of the Rapid Application Development model. These are namely requirements planning, user description, construction, and cutover. Each of them is explained as follows:
This is the very first phase of the Rapid Application Development model. It involves procuring requirements of the software project under development. However, the approach for achieving the aforesaid is what sets the RAD model apart from other software development models.
Unlike other software development models, the very first phase of the RAD model asks for a broad requirement. This broad nature of the requirement enables feeding specific requirements to the project during different points of the development cycle.
For requirements elicitation, a wide array of techniques are used, including brainstorming, FAST (Facilitated Application Development Technique), form analysis, task analysis, and user scenarios.
The requirements planning phase also includes the complete structured plan. It describes:
- The critical data
- The methods for obtaining critical data
- The procedure of processing the critical data to form the final model
User Description/User Design
The second phase of the Rapid Application Development model is the user description. It involves taking user feedback and then building several prototypes of the project under development using developer tools.
Instead of working with a strict set of requirements, RAD developers create a number of prototypes with distinct features and functions. All of these prototypes are then reviewed by the client(s) to decide what to keep what to discard.
The user description phase includes the reexamination and validation of the data collected during the first phase. This phase also includes the identification and elucidation of the dataset attributes.
The construction phase includes the refinement of the prototypes developed in the previous phase. It also includes the use of powerful automated tools for transforming process and data models into the final, operational product.
All the collected enhancements and modifications are applied during this third phase of the RAD approach. Feedback about what is good, what is bad, what to keep, and what to remove, is given in this phase.
The feedback given during the construction phase is not limited to functionality, but also includes aesthetics, interfacing, etc. The prototyping then continues with all the received feedback taken into consideration.
Both prototyping and feedback continue until a final product that fits the client requirements in the most suitable way are developed.
The last phase includes the finalization of the aesthetics, features, functions, interface, and everything else related to the software project. Interfaces between the various independent modules require proper testing. This is done in the cutover phase.
For doing the aforesaid, powerful automated tools are used. It is followed by acceptance testing by the customer. Assuring a desirable level of maintainability, stability, and usability of the developed software is mandatory before delivering the final product to the client.
RAD vs. Other Software Development Models
The Rapid Application Development model differs greatly when compared with other software development models. The RAD model focuses on speed, while most other software development models emphasize delivering a working product to the customer.
Compared to other software development methodologies, a RAD team comprises of fewer members. Hence, communication is clear and fast. Because the RAD approach aims for speed, the development time is less when compared to other approaches.
Most software development models have user input only at the beginning and at the end of the development cycle. However, the RAD model keeps the client(s) involved during the entire process of software development.
- As fewer developers are required, the overall cost of the project is remarkably less
- Customer feedback is available during the initial stages
- Due to the shorter iteration time spans, it is easier to accommodate frequent changes in requirements
- Easy to gauge the development and progress of the software project through different stages
- The total time of the software project under development is significantly reduced due to the use of reusable components
- Use of powerful development tools ensures a better product quality
- The absence of reusable components increases the chances of failure of the project
- Customer involvement is compulsory during the entire life cycle
- More complex to manage when compared to other software development models
- Projects incapable of modularization can’t be developed using this software development model
- The cost of employing powerful automated tools and techniques might exceed the budget of the project for smaller projects. Hence, the software development model is unsuitable for small-scale projects
- The team leader needs to work closely with both the developers as well as the customers to meet the deadline
- Using efficacious and powerful tools necessitates for highly skilled professionals
- Already existent system components that can be used for developing a new system with minimum modifications
- Software development projects with identified requirements that demand a short development time
- Suitable for software development projects where reusable components are available for development and whose requirements can be modularized
- Software projects whose budget considerations allow for the use of automated tools and techniques
The Rapid Application Development model is one of the best software development models available as of now. Due to its evolving nature, it is able to withstand the test of time.
Like other SDLC models, the RAD model has its own advantages and limitations. Underlining all software development project requirements allows picking the best SDLC approach. However, that is where the RAD model really shines.
You need not to entirely sure of all your requirements while beginning with the RAD approach. The software development methodology helps in identifying the requirements alongside the software development process.