Rapid Application Development (RAD) is an incremental software development process model that emphasizes a very short development cycle [typically 60-90 days]. The RAD model, is a high-speed adaptation of the waterfall model, where the result of each cycle a fully functional system.

RAD is used primarily for information systems applications; the RAD approach encompasses the
following phases:

	Business modeling
	Data modeling
	Process modeling
	Application generation
	Testing and turnover
	Top^

This model derives its name from the way in which the software is built. More specifically, the model is designed, implemented and tested as a series of incremental builds until the product is finished. A build consists of pieces of code from various modules that interact together to provide a specific function.

At each stage of the Incremental Model a new build is coded and then integrated into the structure, which is tested as a whole. Note that the product is only defined as finished when it satisfies all of its requirements. This model combines the elements of the waterfall model with the iterative philosophy of prototyping at each stage

	The client assigns a value to each build not yet implemented
	Iblesoft estimates cost of developing each build
	The resulting value-to-cost ratio is the criterion used for selecting which build is delivered next

Essentially the build with the highest value-to-cost ratio is the one that provides the client with the most functionality (value) for the least cost. Using this method Iblesoft’s client has a usable product at all of the development stages.

The spiral model combines the iterative nature of prototyping with the controlled and systematic aspects of the waterfall model, therein providing the potential for rapid development of incremental versions of the software. In this model the software is developed in a series of incremental releases with the early stages being either paper models or prototypes. Later iterations become increasingly more complete versions of the product.

Depending on the model it may have 3-6 task regions (/framework activities) our case will consider a ‘6-task region’ model.

These regions are:

	The customer communication task – to establish effective communication between developer and customer.
	The planning task – to define resources, time lines and other project related information..
	The risk analysis task – to assess both technical and management risks.
	The engineering task – to build one or more representations of the application.
	The construction and release task– to construct, test, install and provide user support (e.g., documentation and training).
	The customer evaluation task – to obtain customer feedback based on the evaluation of the software representation created during the engineering stage and implemented during the install stage.

The evolutionary processbeginsat the center position and moves in a clockwise direction. Each traversal of the spiral typically results in a deliverable. For example, the first and second spiral traversals may result in the production of a product specification and a prototype, respectively. Subsequent traversals may then produce more sophisticated versions of the software.

An important distinction between the spiral model and other software models is the explicit consideration of risk. There are no fixed phases such as specification or design phases in the model and it encompasses other process models. For example, prototyping may be used in one spiral to resolve requirement uncertainties and hence reduce risks. This may then be followed by a conventional waterfall development.