SDLC
Software Development Life Cycle (SDLC)
• It is a process used by the software industry to design,
develop and test high quality softwares.
• Aiming To meets or exceeds customer expectations,
reaches completion within times and cost estimates.
• It is also called as Software Development Process.
• SDLC is a framework defining tasks performed at each step in
the software development process.
• ISO/IEC 12207 is an international standard for software life-
cycle processes. It aims to be the standard that defines all the
tasks required for developing and maintaining software
A detailed plan describing “ How to develop, maintain, replace and alter or enhance
specific software.
The life cycle defines a methodology for improving the quality of software and the
overall development process.
Stage 1: Planning and Requirement Analysis
The most important and fundamental stage in SDLC.
Performed by the senior members of the team with inputs
from the customer, the sales department, market surveys and
domain experts in the industry.
This information is then used to plan the basic project approach
and to conduct product feasibility study in the economical,
operational and technical areas.
• Quality assurance requirements and Risk identification is also
done in the planning stage.
• The outcome of the technical feasibility study is can be followed
to implement the project successfully with minimum risks.
Stage 2: Defining Requirements
The product requirements and get them approved from the customer or the
market analysts. This is done through an SRS (Software Requirement
Specification) document which consists of all the product requirements to be
designed and developed during the project life cycle.
Feasibility study: There are mainly five types of feasibilities checks:
1. Economic: Can we complete the project within the budget or not?
2. Legal: Can we handle this project as cyber law and other regulatory
framework/compliances.
3. Operation feasibility: Can we create operations which is expected by the
client?
4. Technical: Need to check whether the current computer system can support
the software
5. Schedule: Decide that the project can be completed within the given
schedule or not.
Stage 3: Designing the Product Architecture
SRS is the reference for product architects to come out with the best architecture for
the product to be developed.
Based on the requirements specified in SRS, usually more than one design approach for
the product architecture is proposed and documented in a DDS - Design Document
Specification.
This DDS is reviewed by all the important stakeholders
1. Risk assessment,
2. Product robustness,
3. Design modularity,
4. Budget
5. Time constraints, the best design approach is selected for the product.
A design approach clearly defines all the architectural modules of the product along
with its communication and data flow representation with the external and third party
modules (if any).
Developers follow the Organizations coding guidelines and programming tools like
compilers, interpreters, debuggers, etc. with high level programming languages such
as C, C++, Pascal, Java and PHP with respect to the type of software being developed
Stage 5: Testing the Product
Once the software is complete, and it is deployed in the testing
environment.
Functionality Test- This is done to verify that the entire application
works according to the customer requirement.
During this phase, QA and testing team may find some
bugs/defects which they communicate to developers. The
development team fixes the bug and send back to QA for a re-test.
This process continues until the software is bug-free, stable, and
working according to the business needs of that system.
In the modern SDLC models, the testing activities are mostly
involved in all the stages of SDLC.
Stage 6: Deployment in the Market and Maintenance
Once the system is deployed, and customers start using the developed system,
following 3 activities occur
1. Bug fixing - bugs are reported because of some scenarios which are not tested at all
2. Upgrade - Upgrading the application to the newer versions of the Software
3. Enhancement - Adding some new features into the existing software
Once the product is tested and ready to be deployed it is released formally in the
appropriate market. Sometimes product deployment happens in stages as per the
business strategy of that organisation.
The product may first be released in a limited segment and tested in the Real business
environment (UAT- User acceptance testing).
Then based on the feedback, the product may be released as it is or with suggested
enhancements in the targeting market segment. After the product is released in the
market, its maintenance is done for the existing customer base.
SDLC Models
There are various software development life cycle models
Each process model follows a Series of steps unique to its type to ensure success in the
process of software development.
Following are the most important and popular SDLC models followed in the industry −
Waterfall Model The waterfall model is a breakdown of project activities into linear
sequential phases, where each phase depends on the deliverables of the previous
one and corresponds to a specialisation of tasks. The approach is typical for certain
areas of engineering design
Iterative Model
Spiral Model The spiral model is a risk-driven software development process model.
Based on the unique risk patterns of a given project, the spiral model guides a team
to adopt elements of one or more process models, such as incremental, waterfall, or
evolutionary
V-Model
Big Bang Model
Other related methodologies are Agile Model, RAD Model, Rapid Application
Development and Prototyping Models.
SDLC - Waterfall Model
The Waterfall Model was the first Process Model to be introduced. It is also referred to as
a linear-sequential life cycle model. It is very simple to understand and use. In a waterfall
model, each phase must be completed before the next phase can begin and there is no
overlapping in the phases.
The Waterfall model is the earliest SDLC approach that was used for software
development.
Iterative Model - Design
Iterative process starts with a simple implementation of a subset of the software
requirements and iteratively enhances the evolving versions until the full system is
implemented. At each iteration, design modifications are made and new functional
capabilities are added. The basic idea behind this method is to develop a system
through repeated cycles (iterative) and in smaller portions at a time (incremental).
The following illustration is a representation of the Iterative and Incremental model −
Spiral Model – Design
The spiral model has four phases. A software project repeatedly passes through these
phases in iterations called Spirals.
V-Model
Under the V-Model, the corresponding testing phase of the development phase is
planned in parallel. So, there are Verification phases on one side of the ‘V’ and
Validation phases on the other side. The Coding Phase joins the two sides of the V-
Model.
