What is RAD model- advantages, disadvantages and when to use it?

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RAD model is Rapid Application Development model. It is a type of incremental model. In RAD model the components or functions are developed in parallel as if they were mini projects. The developments are time boxed, delivered and then assembled into a working prototype.  This can quickly give the customer something to see and use and to provide feedback regarding the delivery and their requirements.

Diagram of RAD-Model:

The phases in the rapid application development (RAD) model are:

Business modeling: The information flow is identified between various business functions.
Data modeling: Information gathered from business modeling is used to define data objects that are needed for the business.
Process modeling: Data objects defined in data modeling are converted to achieve the business information flow to achieve some specific business objective. Description are identified and created for CRUD of data objects.
Application generation: Automated tools are used to convert process models into code and the actual system.
Testing and turnover: Test new components and all the interfaces.

Advantages of the RAD model:

• Reduced development time.
• Increases reusability of components
• Quick initial reviews occur
• Encourages customer feedback
• Integration from very beginning solves a lot of integration issues.

Disadvantages of RAD model:

• Depends on strong team and individual performances for identifying business requirements.
• Only system that can be modularized can be built using RAD
• Requires highly skilled developers/designers.
• High dependency on modeling skills
• Inapplicable to cheaper projects as cost of modeling and automated code generation is very high.

 When to use RAD model:

• RAD should be used when there is a need to create a system that can be modularized in 2-3 months of time.
• It should be used if there’s high availability of designers for modeling and the budget is high enough to afford their cost along with the cost of automated code generating tools.
• RAD SDLC model should be chosen only if resources with high business knowledge are available and there is a need to produce the system in a short span of time (2-3 months).

What is Prototype model- advantages, disadvantages and when to use it?

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The basic idea here is that instead of freezing the requirements before a design or coding can proceed, a throwaway prototype is built to understand the requirements. This prototype is developed based on the currently known requirements. By using this prototype, the client can get an “actual feel” of the system, since the interactions with prototype can enable the client to better understand the requirements of the desired system.  Prototyping is an attractive idea for complicated and large systems for which there is no manual process or existing system to help determining the requirements. The prototype are usually not complete systems and many of the details are not built in the prototype. The goal is to provide a system with overall functionality.

Diagram of Prototype model:

Advantages of Prototype model:

• Users are actively involved in the development
• Since in this methodology a working model of the system is provided, the users get a better understanding of the system being developed.
• Errors can be detected much earlier.
• Quicker user feedback is available leading to better solutions.
• Missing functionality can be identified easily
• Confusing or difficult functions can be identified
  Requirements validation, Quick implementation of, incomplete, but
  functional, application.

Disadvantages of Prototype model:

• Leads to implementing and then repairing way of building systems.
• Practically, this methodology may increase the complexity of the system as scope of the system may expand beyond original plans.
• Incomplete application may cause application not to be used as the
  full system was designed
  Incomplete or inadequate problem analysis.

When to use Prototype model:  

• Prototype model should be used when the desired system needs to have a lot of interaction with the end users.
• Typically, online systems, web interfaces have a very high amount of interaction with end users, are best suited for Prototype model. It might take a while for a system to be built that allows ease of use and needs minimal training for the end user.
• Prototyping ensures that the end users constantly work with the system and provide a feedback which is incorporated in the prototype to result in a useable system. They are excellent for designing good human computer interface systems.