RAD Development Process Model

The Rapid Application Development (RAD) Model is proposed when requirements and solutions can be modularized as independent system or software components, each of which can be developed by different teams. After these smaller system components are developed, they are integrated to produce the large software system solution. The modularization could be on a functional, technology, or architectural basis, such as front-end-back-end, client side-server side, and so on.
Rapid Application Development becomes faster if the software engineer uses the component’s technology such that the components are really available for reuse. Since the development is distributed into component-development teams, the teams work in tandem and total development is completed in a short period (i.e., 60 to 90 days). Figure rd.01 shows the RAD model.

Figure rd.01 RAD Development Process Model

Business Modeling. It covers the following functions: - Where does information come from and go?
- Who processes it?
- What information drives the business process?
- What information is generated?

Data Modeling. The information flow defined as part of the business modeling phase is refined into a set of data objects that are needed to support the business. The characteristics of each object are identified and the relationships between these objects are defined.

Process Modeling. In this model, information flows from object to object to implement a business function. To add, modify, delete, or retain a data object, there is a need for description which is done in this phase.



Application Generation. RAD assumes the use of fourth-generation techniques. The RAD process works to reuse existing program components or create reusable components. To facilitate the construction of the software using the above cases, automated tools are used.

Testing and Turnover. In this phase we have to test the programs, but we use some already existing programs which are already tested, so the time involved in testing is less. Only the new programs or components must be tested.

Many business applications rely on structured forms for input and output, so RAD environments provide powerful facilities for screen definition and report generation. Screens are often defined as a series of linked forms (in one application we studied, there were 137 form definitions) so the screen generation system must provide for:

1. Interactive form definition where the developer defines the fields to be displayed and how these are to be organised.
2. Form linking where the developer can specify that particular inputs cause further forms to be displayed.
3. Field verification where the developer defines allowed ranges for values input to form fields.

RAD systems are successful because there is a greatdeal of commonality across business applications. In essence, these applications are often concerned with updating a database and producing reports from the information in the database. Standard forms are used for input and output. RAD systems are geared towards producing interactive applications that rely on abstracting information from an organisational database, presenting it to end-users on their terminal or workstation, and updating the database with changes made by users.

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