SOFTWARE MODELS-4

RAD MODEL



Rapid application development (RAD) is an incremental software development process
model that emphasizes an extremely short development cycle. The RAD model is a
“high-speed” adaptation of the linear sequential model in which rapid development
is achieved by using component-based construction. If requirements are well understood
and project scope is constrained, the RAD process enables a development team
to create a “fully functional system” within very short time periods.Used primarily for information systems applications, the RAD approach
encompasses the following phases.
Business modeling. The information flow among business functions is modeled in
a way that answers the following questions: What information drives the business
process? What information is generated? Who generates it? Where does the information
go? Who processes it?
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 char-

acteristics (called attributes) of each object are identified and the relationships between
these objects defined.

Process modeling. The data objects defined in the data modeling phase are transformed
to achieve the information flow necessary to implement a business function.
Processing descriptions are created for adding, modifying, deleting, or retrieving a
data object.
Application generation. RAD assumes the use of fourth generation techniques
. Rather than creating software using conventional third generation
programming languages the RAD process works to reuse existing program components
(when possible) or create reusable components (when necessary). In all cases,
automated tools are used to facilitate construction of the software.
Testing and turnover. Since the RAD process emphasizes reuse, many of the program
components have already been tested. This reduces overall testing time. However,
new components must be tested and all interfaces must be fully exercised.The RAD process model is illustrated in Figure. Obviously, the time constraints
imposed on a RAD project demand “scalable scope” . If a business application
can be modularized in a way that enables each major function to be completed
in less than three months (using the approach described previously), it is a candidate
for RAD. Each major function can be addressed by a separate RAD team and then
integrated to form a whole.
Like all process models, the RAD approach has drawbacks :
• For large but scalable projects, RAD requires sufficient human resources to
create the right number of RAD teams.
• RAD requires developers and customers who are committed to the rapid-fire
activities necessary to get a system complete in a much abbreviated time
frame. If commitment is lacking from either constituency, RAD projects will
fail.
• Not all types of applications are appropriate for RAD. If a system cannot be
properly modularized, building the components necessary for RAD will be
problematic. If high performance is an issue and performance is to be
achieved through tuning the interfaces to system components, the RAD
approach may not work.
• RAD is not appropriate when technical risks are high. This occurs when a new
application makes heavy use of new technology or when the new software
requires a high degree of interoperability with existing computer programs.