RAD (Rapid Application Development) is probably the most popular type of SDLC model today. With this development model, developers are able to build an application really fast. Basically RAD lets the developers constantly build an application by stages while consulting to the potential users. With that technique, developers does not only cuts the testing stage but they also ensure that the application are built according to the specification of the future users. This type of SDLC development model should be implemented in all web and application languages and that includes Ajax. Unfortunately, Ajax is notoriously popular because it forces the developers to learn not only a single language but a series of languages. JavaScript, XML and HTTP are only three of the applications that you have to learn if you want to build a good looking application.