The Following are the basic popular models used by many software
development firms.
a) System Development Life Cycle (SDLC) Model
b) Prototyping Model
c) Rapid Application Development Model
d) Component Assembly Model
System Development Life
Cycle Model (SDLC Model)
This is also known as Classic Life Cycle Model (or) Linear Sequential Model
(or) Waterfall Method. This has the following activities.
1. System/Information Engineering and Modeling
2. Software Requirements Analysis
3. Systems Analysis and Design
4. Code Generation
5. Testing
6. Maintenance
System/Information
Engineering and Modeling
As software is always of a large system (or business), work begins by
establishing requirements for all system elements and then allocating some
subset of these requirements to software. This system view is essential when
software must interface with other elements such as hardware, people and
other resources. System is the basic and very critical requirement for the
existence of software in any entity. So if the system is not in place, the
system should be engineered and put in place. In some cases, to extract the
maximum output, the system should be re-engineered and spruced up. Once the
ideal system is engineered or tuned, the development team studies the
software requirement for the system.
Software Requirement
Analysis
This is also known as feasibility study. In this phase, the development team
visits the customer and studies their system. They investigate the need for
possible software automation in the given system. By the end of the
feasibility study, the team furnishes a document that holds the different
specific recommendations for the candidate system. It also includes the
personnel assignments, costs, project schedule, and target dates. The
requirements gathering process is intensified and focussed specially on
software. To understand the nature of the program(s) to be built, the system
engineer ("analyst") must understand the information domain for the
software, as well as required function, behavior, performance and
interfacing. The essential purpose of this phase is to find the need and to
define the problem that needs to be solved .
System Analysis and
Design
In this phase, the software development process, the software's overall
structure and its nuances are defined. In terms of the client/server
technology, the number of tiers needed for the package architecture, the
database design, the data structure design etc are all defined in this
phase. A software development model is created. Analysis and Design are very
crucial in the whole development cycle. Any glitch in the design phase could
be very expensive to solve in the later stage of the software development.
Much care is taken during this phase. The logical system of the product is
developed in this phase.
Code Generation
The design must be translated into a machine-readable form. The code
generation step performs this task. If the design is performed in a detailed
manner, code generation can be accomplished without much complication.
Programming tools like Compilers, Interpreters, Debuggers are used to
generate the code. Different high level programming languages like C, C++,
Pascal, Java are used for coding. With respect to the type of application,
the right programming language is chosen.
Testing
Once the code is generated, the software program testing begins. Different
testing methodologies are available to unravel the bugs that were committed
during the previous phases. Different testing tools and methodologies are
already available. Some companies build their own testing tools that are
tailor made for their own development operations.
Maintenance
Software will definitely undergo change once it is delivered to the
customer. There are many reasons for the change. Change could happen because
of some unexpected input values into the system. In addition, the changes in
the system could directly affect the software operations. The software
should be developed to accommodate changes that could happen during the post
implementation period.
Back to top
Prototyping Model
This is a cyclic version of the linear model. In this model, once the
requirement analysis is done and the design for a prototype is made, the
development process gets started. Once the prototype is created, it is given
to the customer for evaluation. The customer tests the package and gives
his/her feed back to the developer who refines the product according to the
customer's exact expectation. After a finite number of iterations, the final
software package is given to the customer. In this methodology, the software
is evolved as a result of periodic shuttling of information between the
customer and developer. This is the most popular development model in the
contemporary IT industry. Most of the successful software products have been
developed using this model - as it is very difficult (even for a whiz kid!)
to comprehend all the requirements of a customer in one shot. There are many
variations of this model skewed with respect to the project management
styles of the companies. New versions of a software product evolve as a
result of prototyping.
Back to top
Rapid Application
Development (RAD) Model
The RAD is a linear sequential software development process that emphasizes
an extremely short development cycle. The RAD software model is a "high
speed" adaptation of the linear sequential model in which rapid development
is achieved by using a component-based construction approach. 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 characteristic (called attributes) of each object is
identified and the relationships between these objects are 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 the descriptions are created for adding, modifying, deleting,
or retrieving a data object.
- Application generation
RAD assumes the use of the RAD tools like VB, VC++, Delphi etc rather
than creating software using conventional third generation programming
languages. The RAD 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 minimizes the testing and development
time.
Back to top
Component Assembly Model
Object technologies provide the technical framework for a component-based
process model for software engineering. The object oriented paradigm
emphasizes the creation of classes that encapsulate both data and the
algorithm that are used to manipulate the data. If properly designed and
implemented, object oriented classes are reusable across different
applicationsand computer based system architectures. Component Assembly
Model leads to software reusability. The integration/assembly of the already
existing software components accelerate the development process. Nowadays
many component libraries are available on the Internet. If the right
components are chosen, the integration aspect is made much simpler.
Conclusion
All these different software development models have their own advantages
and disadvantages. Nevertheless, in the contemporary commercial software
evelopment world, the fusion of all these methodologies is incorporated.
Timing is very crucial in software development. If a delay happens in the
development phase, the market could be taken over by the competitor. Also if
a 'bug' filled product is launched in a short period of time (quicker than
the competitors), it may affect the reputation of the company. So, there
should be a tradeoff between the development time and the quality of the
product. Customers don't expect a bug free product but they expect a
user-friendly product. That results in Customer Ecstasy!
