What is Agile Model

The Agile Model is a type of project management and software development approach that is characterized by its iterative, incremental, and collaborative nature. It breaks down larger projects into small, manageable chunks known as iterations or sprints.

This model provides a highly flexible and interactive method of software development, and because of its iterative nature, the changes can be incorporated at any time during the project development process. As such, it's particularly valuable in projects where the requirements are expected to change or are not fully known at the start.

Comparison to Waterfall Model

The Waterfall Model, one of the earliest software development methodologies, follows a linear, sequential approach. Each phase of the project—Concept, Initiation, Analysis, Design, Construction, Testing, Implementation, and Maintenance—must be completed before the next begins, making it easy to manage and understand. It's often used in projects where the scope, requirements, and technology are well-understood.

On the other hand, the Agile model adopts an iterative approach. Agile accepts that software requirements are prone to changes, even late in development, and focuses on delivering small, working parts of the software application as quickly as possible. These mini releases ensure the product remains aligned with changing customer needs and business objectives.

While the Waterfall Model promotes rigidity and discipline, Agile Model prioritizes adaptability and customer satisfaction. In Agile, changes in scope, schedule, and resources are expected and embraced, whereas, in Waterfall, changes often result in project delays and increased costs.

Advantages and Disadvantages of Agile Model

The Agile Model provides numerous benefits, making it a popular choice among many organizations. Here are some notable advantages:

• Improved Customer Satisfaction
  Agile involves stakeholders and customers throughout the project, providing opportunities for feedback and ensuring the end product meets expectations.
• Increased Flexibility
  The Agile model embraces change, even late in development, allowing the project to adapt to evolving requirements.
• Enhanced Quality Control
  By breaking the project into manageable units, teams can focus on high-quality development, testing, and collaboration.
• Risk Mitigation
  Regular iterations and frequent testing allow potential issues to be identified and addressed early on.

Despite these advantages, the Agile Model also has its share of disadvantages:

• Limited Documentation
  Agile methodology often lacks detailed predictive documentation since the focus is more on delivering a working product.
• Requires Expertise
  Agile requires a team capable of interpreting customer requirements into a final product without extensive documentation.
• Increased Dependency on Customer/Stakeholder Involvement
  If the customer or stakeholder is not clear about the final outcome, the project may deviate from its original goal.
• Scope Creep
  Without careful control, the scope of the project can easily expand beyond its original objectives.

Key Terms of Agile Model

Understanding the Agile model's terminology is vital for effective implementation and communication within the team. Here are some of the commonly used terms:

User Story

In the Agile model, a User Story is a simple, clear, and short description of a software feature, expressed from the perspective of an end-user. It helps to create a simplified description of a requirement, focusing on the value or the benefit the user gets from this feature. User Stories often follow a structure like:

As a [type of user], I want [an action] so that [a benefit or value].

Iteration (Sprint)

An Iteration or Sprint is a defined time period (typically between one to four weeks) during which a specific set of work has to be completed and made ready for review. During an iteration, teams will develop, test, and deliver a discrete product increment.

Velocity

Velocity is a key metric in Agile that helps estimate the amount of work a team can handle in a single iteration or sprint. It measures the number of user stories (or story points, another common Agile metric) a team can complete in an iteration. Velocity helps in planning future sprints by providing an average rate of team productivity.

Release Plan

A Release Plan is a roadmap that outlines when product increments should be released to customers. It details the features and functionality to be delivered, highlighting the iterations in which the releases will occur. Release plans are revisited and revised at the end of each iteration based on the team's velocity and any changes in project scope.

Steps of Agile Model

While Agile methodologies are flexible and can be adapted to suit the needs of individual projects, there are some common steps that all Agile projects go through:

1. Project Planning
   Identify the high-level objectives, scope, and infrastructure of the project.

2. Product Roadmap Creation
   Outline the overall project requirements and features, broken down into manageable units (typically user stories).

3. Release Planning
   Determine a timeline for the release of product increments, taking into account the project scope and team's velocity.

4. Sprint Planning
   Plan the activities for the next sprint based on priority of the user stories.

5. Daily Standups
   Short meetings where team members update each other on their progress and discuss any obstacles.

6. Sprint Review and Retrospective
   At the end of each sprint, review the work completed and not completed, and identify ways to improve the process.

7. Next Sprint Planning
   Based on the review and retrospective, begin planning for the next sprint, returning to step 4.

This iterative process continues until the product is ready for release.

Types of Agile Model

There are several specific methodologies under the umbrella of the Agile model, each with its unique approach but upholding the core principles of Agile.

Scrum

Scrum is a popular Agile methodology, characterized by its short, time-boxed iterations (called sprints) and team roles, which include the Product Owner, Scrum Master, and Development Team. It places a strong emphasis on transparency, inspection, and adaptation.

Extreme Programming (XP)

Extreme Programming (XP) focuses on producing high-quality software that meets changing customer needs. It emphasizes teamwork, customer involvement, rapid feedback, and iterative planning and development.

Feature-Driven Development (FDD)

FDD is a model-driven Agile methodology that emphasizes the delivery of tangible, working software in a timely manner. It breaks the project into individual features, which are developed and built upon in each iteration.

Kanban

Kanban is an Agile methodology that emphasizes continuous improvement, productivity, and efficiency. It uses a visual board (Kanban board) to visualize the flow of work, and limits the amount of work in progress to reduce the time it takes for a task to move from the start to the finish. The goal is to identify bottlenecks in the process and fix them, so work can flow through the system unhindered.