The V-Model, also called the Vee-Model, is a product-development process originally developed in Germany for government defense projects. It has become a common standard in software development. The V-Model gets its name from the fact that the process is often mapped out as a flowchart that takes the form of the letter V.
The development process proceeds from the upper left point of the V toward the right, ending at the upper right point. In the left-hand, downward-sloping branch of the V, development personnel define business requirements, application design parameters and design processes. At the base point of the V, the code is written. In the right-hand, upward-sloping branch of the V, testing and debugging is done. The unit testing is carried out first, followed by bottom-up integration testing. The extreme upper right point of the V represents product release and ongoing support.
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.