Agile software development
is a group of software development methods
in which requirements and solutions evolve through collaboration between
self-organizing, cross-functional teams. It promotes
adaptive planning, evolutionary development, early delivery, continuous
improvement, and encourages rapid and flexible response to change. The Manifesto
for Agile Software Development also known as the Agile Manifesto, which first
laid out the underlying concepts of agile development, introduced the term in
2001.
Agile SDLC model is a
combination of iterative and incremental process models with focus on process
adaptability and customer satisfaction by rapid delivery of working software
product.
What is Agile?
Agile model believes that
every project needs to be handled differently and the existing methods need to
be tailored to best suit the project requirements. In agile the tasks are
divided to time boxes (small time frames) to deliver specific features for a
release. Iterative approach is taken and working software build is delivered
after each iteration. Each build is incremental in terms of features; the final
build holds all the features required by the customer.
Graphical illustration of the Agile Model:
Agile Development Model |
Agile Vs Traditional SDLC Models:
Agile is based on the adaptive software development
methods where as the traditional SDLC models like waterfall model is based on
predictive approach. Predictive teams in the traditional SDLC models usually
work with detailed planning and have a complete forecast of the exact tasks and
features to be delivered in the next few months or during the product life
cycle. Predictive methods entirely depend on the requirement analysis and
planning done in the beginning of cycle. Any changes to be incorporated go
through a strict change control management and prioritization.
Agile uses adaptive approach where there is no detailed
planning and there is clarity on future tasks only in respect of what features
need to be developed. There is feature driven development and the team adapts
to the changing product requirements dynamically. The product is tested very
frequently, through the release iterations, minimizing the risk of any major
failures in future.
Customer
interaction is the backbone of Agile methodology, and open communication with
minimum documentation are the typical features of Agile development
environment. The agile teams work in close collaboration with each other and
are most often located in the same geographical location.
The Agile Manifesto is based on 12 principles:
- Customer satisfaction by rapid delivery of useful software
- Welcome changing requirements, even late in development
- Working software is delivered frequently (weeks rather than months)
- Close, daily cooperation between business people and developers
- Projects are built around motivated individuals, who should be trusted
- Face-to-face conversation is the best form of communication (co-location)
- Working software is the principal measure of progress
- Sustainable development, able to maintain a constant pace
- Continuous attention to technical excellence and good design
- Simplicity—the art of maximizing the amount of work not done—is essential
- Self-organizing teams
- Regular adaptation to changing circumstance
Advantages of Agile model:
- Customer satisfaction by rapid, continuous delivery of useful software.
- People and interactions are emphasized rather than process and tools. Customers, developers and testers constantly interact with each other.
- Working software is delivered frequently (weeks rather than months).
- Face-to-face conversation is the best form of communication.
- Close, daily cooperation between business people and developers.
- Continuous attention to technical excellence and good design.
- Regular adaptation to changing circumstances.
- Even late changes in requirements are welcomed
Disadvantages of Agile model:
- In case of some software deliverable, especially the large ones, it is difficult to assess the effort required at the beginning of the software development life cycle.
- There is lack of emphasis on necessary designing and documentation.
- The project can easily get taken off track if the customer representative is not clear what final outcome that they want.
- Only senior programmers are capable of taking the kind of decisions required during the development process. Hence it has no place for newbie programmers, unless combined with experienced resources.
When to use Agile model:
- When new changes are needed to be implemented. The freedom agile gives to change is very important. New changes can be implemented at very little cost because of the frequency of new increments that are produced.
- To implement a new feature the developers need to lose only the work of a few days, or even only hours, to roll back and implement it.
- Unlike the waterfall model in agile model very limited planning is required to get started with the project. Agile assumes that the end users’ needs are ever changing in a dynamic business and IT world. Changes can be discussed and features can be newly affected or removed based on feedback. This effectively gives the customer the finished system they want or need.
- Both system developers and stakeholders alike, find they also get more freedom of time and options than if the software was developed in a more rigid sequential way. Having options gives them the ability to leave important decisions until more or better data or even entire hosting programs are available; meaning the project can continue to move forward without fear of reaching a sudden standstill.
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