Agile model

The agile model is an iterative and incremental approach to software development that values flexibility, customer collaboration and quick delivery of working software. It is based on the Agile Manifesto (2001).

Agile Manifesto values

• Individuals and interactions over processes and tools.
• Working software over comprehensive documentation.
• Customer collaboration over contract negotiation.
• Responding to change over following a plan.

Principles

Early and continuous delivery, welcome changing requirements, frequent delivery in weeks, daily cooperation between business and developers, motivated teams, face-to-face communication, working software as the main measure of progress, sustainable pace, simplicity and regular reflection.

Process (Scrum example)

Product backlog -> Sprint planning -> Sprint (2-4 wks)
       ^                                 |  daily scrum
       |                                 v
   Feedback <- Sprint review <- Working increment

• Roles: Product Owner, Scrum Master, Development Team.
• Artifacts: product backlog, sprint backlog, increment.
• Events: sprint planning, daily stand-up, sprint review, retrospective.

Other agile methods: Extreme Programming (XP), Kanban, Crystal, FDD.

Advantages

• Quick delivery and early feedback.
• Handles changing requirements well.
• High customer involvement and satisfaction.
• Reduced risk through small increments.

Disadvantages

• Hard to predict final cost and time for large projects.
• Needs experienced, self-organised team and constant user availability.
• Less documentation can create maintenance problems.
• Difficult with fixed-price contracts.

Example: A startup builds a food-delivery app in two-week sprints, releasing ordering first and adding payment and tracking later based on user feedback.