Software Development Life Cycle,
SDLC Activities
SDLC provides a series of steps to be followed to design and develop a
software product efficiently. SDLC framework includes the following
steps:
Communication
This is the first step where the user initiates the request for a
desired software product. He contacts the service provider and tries to
negotiate the terms. He submits his request to the service providing
organization in writing.
Requirement Gathering
This step onwards the software development team works to carry on the
project. The team holds discussions with various stakeholders from
problem domain and tries to bring out as much information as possible on
their requirements. The requirements are contemplated and segregated
into user requirements, system requirements and functional requirements.
The requirements are collected using a number of practices as given -
- studying the existing or obsolete system and software,
- conducting interviews of users and developers,
- referring to the database or
- collecting answers from the questionnaires.
Feasibility Study
After requirement gathering, the team comes up with a rough plan of
software process. At this step the team analyzes if a software can be
made to fulfill all requirements of the user and if there is any
possibility of software being no more useful. It is found out, if the
project is financially, practically and technologically feasible for the
organization to take up. There are many algorithms available, which
help the developers to conclude the feasibility of a software project.
System Analysis
At this step the developers decide a roadmap of their plan and try to
bring up the best software model suitable for the project. System
analysis includes Understanding of software product limitations,
learning system related problems or changes to be done in existing
systems beforehand, identifying and addressing the impact of project on
organization and personnel etc. The project team analyzes the scope of
the project and plans the schedule and resources accordingly.
Software Design
Next step is to bring down whole knowledge of requirements and
analysis on the desk and design the software product. The inputs from
users and information gathered in requirement gathering phase are the
inputs of this step. The output of this step comes in the form of two
designs; logical design and physical design. Engineers produce meta-data
and data dictionaries, logical diagrams, data-flow diagrams and in some
cases pseudo codes.
Coding
This step is also known as programming phase. The implementation of
software design starts in terms of writing program code in the suitable
programming language and developing error-free executable programs
efficiently.
Testing
An estimate says that 50% of whole software development process
should be tested. Errors may ruin the software from critical level to
its own removal. Software testing is done while coding by the developers
and thorough testing is conducted by testing experts at various levels
of code such as module testing, program testing, product testing,
in-house testing and testing the product at user’s end. Early discovery
of errors and their remedy is the key to reliable software.
Integration
Software may need to be integrated with the libraries, databases and
other program(s). This stage of SDLC is involved in the integration of
software with outer world entities.
Implementation
This means installing the software on user machines. At times,
software needs post-installation configurations at user end. Software is
tested for portability and adaptability and integration related issues
are solved during implementation.
Operation and Maintenance
This phase confirms the software operation in terms of more
efficiency and less errors. If required, the users are trained on, or
aided with the documentation on how to operate the software and how to
keep the software operational. The software is maintained timely by
updating the code according to the changes taking place in user end
environment or technology. This phase may face challenges from hidden
bugs and real-world unidentified problems.
Disposition
As time elapses, the software may decline on the performance front.
It may go completely obsolete or may need intense upgradation. Hence a
pressing need to eliminate a major portion of the system arises. This
phase includes archiving data and required software components, closing
down the system, planning disposition activity and terminating system at
appropriate end-of-system time.
Software Development Paradigm
The software development paradigm helps developer to select a
strategy to develop the software. A software development paradigm has
its own set of tools, methods and procedures, which are expressed
clearly and defines software development life cycle. A few of software
development paradigms or process models are defined as follows:
Waterfall Model
Waterfall model is the simplest model of software development
paradigm. It says the all the phases of SDLC will function one after
another in linear manner. That is, when the first phase is finished then
only the second phase will start and so on.
This model assumes that everything is carried out and taken place
perfectly as planned in the previous stage and there is no need to think
about the past issues that may arise in the next phase. This model does
not work smoothly if there are some issues left at the previous step.
The sequential nature of model does not allow us go back and undo or
redo our actions.
This model is best suited when developers already have designed and
developed similar software in the past and are aware of all its domains.
Iterative Model
This model leads the software development process in iterations. It
projects the process of development in cyclic manner repeating every
step after every cycle of SDLC process.
The software is first developed on very small scale and all the steps
are followed which are taken into consideration. Then, on every next
iteration, more features and modules are designed, coded, tested and
added to the software. Every cycle produces a software, which is
complete in itself and has more features and capabilities than that of
the previous one.
After each iteration, the management team can do work on risk
management and prepare for the next iteration. Because a cycle includes
small portion of whole software process, it is easier to manage the
development process but it consumes more resources.
Spiral Model
Spiral model is a combination of both, iterative model and one of the
SDLC model. It can be seen as if you choose one SDLC model and combine
it with cyclic process (iterative model).
This model considers risk, which often goes un-noticed by most other
models. The model starts with determining objectives and constraints of
the software at the start of one iteration. Next phase is of prototyping
the software. This includes risk analysis. Then one standard SDLC model
is used to build the software. In the fourth phase of the plan of next
iteration is prepared.
V – model
The major drawback of waterfall model is we move to the next stage
only when the previous one is finished and there was no chance to go
back if something is found wrong in later stages. V-Model provides means
of testing of software at each stage in reverse manner.
At every stage, test plans and test cases are created to verify and
validate the product according to the requirement of that stage. For
example, in requirement gathering stage the test team prepares all the
test cases in correspondence to the requirements. Later, when the
product is developed and is ready for testing, test cases of this stage
verify the software against its validity towards requirements at this
stage.
This makes both verification and validation go in parallel. This model is also known as verification and validation model.
Big Bang Model (TIME EFFORT RESOURCES)
This model is the simplest model in its form. It requires little
planning, lots of programming and lots of funds. This model is
conceptualized around the big bang of universe. As scientists say that
after big bang lots of galaxies, planets and stars evolved just as an
event. Likewise, if we put together lots of programming and funds, you
may achieve the best software product.
For this model, very small amount of planning is required. It does
not follow any process, or at times the customer is not sure about the
requirements and future needs. So the input requirements are arbitrary.
This model is not suitable for large software projects but good one for learning and experimenting.
