Agile Model in Software Engineering

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The digital world's increasing need for complex software applications has led to a high failure rate in software development projects. The traditional Iterative Waterfall approach faced challenges in handling customer change requests, which were time-consuming and expensive. In 2001, the Agile model in Software engineering emerged as a solution. Agile was initially designed for software development but has now expanded to manage projects across different industries and markets.

What is Agile Model in Software Engineering?

Agile refers to something quick or adaptable. The Agile model is an SDLC model focused on iterative software product development. The Agile paradigm is an incremental model in which software is built in quick increments. The most significant aspect of the Agile model is determining the project scope, requirements, number, and duration of iterations at the start of the development process.

Types of Agile Model in Software Engineering

1. Scrum

It is the most popular variant of the agile methodology. It is a team-based agile development process that focuses on task management. It encourages collaboration in small groups and believes in empowering the development team. Each iteration of a scrum is termed a Sprint.

A scrum team has three key positions, each with its own set of responsibilities, which are outlined below:

Developers: Team members that actually complete the Product Increment during the Sprint. Scrum Master: Sets up the team, leads sprint meetings, and removes development impediments. Product Owner: Creates the product backlog, prioritizes delays, and is in charge of distributing functionality on each iteration. The Scrum Team organizes and supervises their work to complete the sprint or cycle.

2. Crystal

Crystal is an Agile model that focuses on adapting the software development process to the project's unique characteristics. It offers a set of methodologies, such as Crystal Clear, Crystal Yellow, Crystal Orange, and more, based on project size, priorities, and team dynamics. Crystal emphasizes communication, reflection, and frequent delivery of working software. It aims to strike a balance between formal processes and flexibility to ensure project success.

3. Dynamic Software Development Method (DSDM)

DSDM is an Agile model that provides an iterative and incremental framework for software development. It emphasizes active user involvement throughout the project and places a strong emphasis on delivering business value. DSDM promotes collaboration, prototyping, and continuous feedback from stakeholders. It includes phases like feasibility study, business study, functional model iteration, design and build iteration, and implementation.

4. Feature Driven Development (FDD)

FDD is an Agile model that focuses on feature-centric development. It involves breaking down the project into small, manageable features that can be developed independently. FDD emphasizes domain object modeling, iterative and incremental development, and regular progress reporting. It utilizes roles like the Chief Architect, Development Manager, and Feature Owner to ensure effective feature delivery.

5. Lean Software Development

Lean Software Development is an Agile model inspired by lean manufacturing principles. It aims to eliminate waste, optimize flow, and maximize value delivery. Lean focuses on continuous improvement, customer collaboration, and quick feedback cycles. It encourages practices such as value stream mapping, just-in-time development, and continuous delivery.

6. eXtreme Programming (XP)

eXtreme Programming is an Agile model that emphasizes customer satisfaction, teamwork, and high-quality software. XP promotes short development cycles, frequent customer feedback, and continuous testing. It encourages practices like pair programming, test-driven development, continuous integration, and collective code ownership.

Phases of the Agile Model


Following are the Agile Model phases:

  • Requirements gathering
  • Design the requirements
  • Development/iteration
  • Testing/Quality assurance
  • Deployment
  • Feedback

Requirement Gathering

In this stage, the project's critical needs are specified. This stage discusses the key features and plans the project's time and effort. At this point, the team must establish the criteria. They should define the business potential for the project and quantify the time and effort needed to complete it. Based on these data, you can examine technical and economic feasibility.

Design the Requirement

Once the project requirements have been gathered, the development team must collaborate with stakeholders to design requirements. A user flow diagram or a high-level UML diagram can be used to demonstrate the functionality of new features and how they will interact with the existing system.


The real effort begins after the team specifies and designs the requirements. After the requirements have been gathered and defined clearly, the software developers begin working on projects with the goal of creating a viable product. All of this occurs throughout an iteration or sprint. Before being released, the product will go through multiple rounds of development.

Testing/Quality Assurance

In this phase, the QA team tests the product's performance and looks for bugs in the code.


In this phase, the team creates a product for the user's work environment.


This phase involves taking feedback from the users after the product has been released. The team may need to implement changes if necessary.

Iteration of the Agile Model in Software Engineering

An Agile iteration is a short period of time in which a piece of work is developed and tested. Each iteration has a deadline by which all deliverables must be completed. Iterations are the fundamental building element of Agile development. They usually last from one to four weeks. Each iteration yields minor incremental releases that build on previous capabilities. This individual release is rigorously tested to maintain the software's quality.

The entire project is divided into smaller portions or sprints with Agile to reduce project delivery time and hazards. An iteration requires a team to go through the entire software development cycle. Within a single iteration, an Agile team will

  1. map out the requirements
  2. develop the user stories
  3. test their software
  4. produce an end deliverable
  5. request for user feedback.

Applications of the Agile Model

The Agile model was primarily conceived to help a project adapt quickly to changing requests. So, the main aim of the Agile model is to enable quick project completion.

To accomplish this task, agility is required. Agility is achieved by fitting the process to the project and removing activities that may not be essential for a specific project. Also, anything that is a waste of time and effort is avoided. Agile finds applications in various medium to large software projects.

When to Use the Agile Model?

  • Agile is helpful when there is a need for implementing new changes as the flexibility provided by the Agile model becomes crucial.
  • It is helpful when frequent addition of new features is needed at minimal cost in agile.
  • Developers can easily roll back and incorporate new features, typically requiring only a few days or even hours of work.
  • Agile is suitable when project requirements are expected to change or evolve over time.
  • Agile is well-suited for projects that require rapid and incremental delivery of usable software.
  • Agile is effective for complex and innovative projects that require an iterative and adaptive approach.
  • Agile works best with cross-functional teams, fostering collaboration and shared ownership.

Advantages of the Agile Model

  • Here are some advantages of the agile methodology:
  • Continuous delivery
  • Encourages one-on-one communication with clients
  • Changes in requirements can be accommodated at any moment
  • Reduced development time.
  • Efficient and fulfilling business standards.

Disadvantages of the Agile Model

  • Here are some disadvantages of the agile methodology:
  • It depends heavily on customer interaction, so the team can be driven in the wrong direction if the customer is unclear about their requirements.
  • Due to the absence of proper documentation, maintenance of the developed project can become a problem when the project is completed and the developers are assigned to another project. As a result, there is a very high individual dependency. Transfer of technology to new team members may be pretty tricky. Hence, maintenance can be challenging.
  • Because of the lack of official records, there can be misunderstandings, and crucial decisions made during various phases can be misunderstood at any point by different team members.

Agile model vs Waterfall model

Agile ModelWaterfall Model
The Agile model follows an iterative and incremental development approach, allowing for continuous improvement and adaptation.The Waterfall model follows a sequential development approach, with each phase completed before moving to the next.
The Agile model encourages customer collaboration and feedback, ensuring continuous customer involvement in the development process.The Waterfall model involves limited customer involvement during the development phase, with less frequent opportunities for feedback.
The Agile model focuses on regular and frequent delivery of usable software increments.The Waterfall model delivers the final software product at the end of the project.
In the Agile model, testing and quality assurance are integrated throughout the development process, ensuring continuous improvement of the software.In the Waterfall model, testing typically occurs at the end of the development process, after all other stages are completed.
The Agile model is suitable for projects with evolving requirements and a need for adaptability and responsiveness to change.The Waterfall model is suitable for projects with well-defined requirements and a focus on stability and predictability.


  • The Agile methodology makes the most sense when frequent changes are expected, and a highly competent and experienced team is available. Because of the regularity with which new increments are produced, the cost of implementing the necessary changes is relatively low.
  • When developing software products using the Agile methodology, both the developer and the client have more time and options than if the software product was built more traditionally.