While each of the agile methodologies is unique in its specific approach, they all share a common vision and core values (see the Agile Manifesto). They all fundamentally incorporate iteration and the continuous feedback that it provides to successively refine and deliver a software system. They all involve continuous planning, continuous testing, continuous integration, and other forms of continuous evolution of both the project and the software. They are all lightweight, especially compared to traditional waterfall-style processes, and inherently adaptable. What is more important about agile methods is that they all focus on empowering people to collaborate and make decisions together quickly and effectively.
''Agile Development'' is an umbrella term for several iterative and incremental software development methodologies. The most popular agile methodologies include Extreme Programming (XP), Scrum, Crystal, Dynamic Systems Development Method (DSDM), Lean Development, and Feature-Driven Development (FDD).
The V-Model has gained acceptance because of its simplicity and straightforwardness. However, some developers believe it is too rigid for the evolving nature of IT (information technology) business environments.
The V-Model is a unique, linear development methodology used during a software development life cycle (SDLC). The V-Model focuses on a fairly typical waterfall-esque method that follows strict, step-by-step stages. While initial stages are broad design stages, progress proceeds down through more and more granular stages, leading into implementation and coding, and finally back through all testing stages prior to completion of the project.