prototype that looks like the goal system, but does not provide any functionality. The usage of storyboards, animatics or drawings is not exactly the same as throwaway prototyping, but certainly falls within the same family. These are non-functional implementations but show how the system will look. Summary: In this approach the prototype is constructed with the idea that it will be discarded and the final system will be built from scratch. The steps in this approach are: Write preliminary requirements Design the prototype User experiences/uses the prototype, specifies new requirements Repeat if necessary Write the final requirements Evolutionary prototyping Evolutionary prototyping (also known as breadboard prototyping) is quite different from throwaway prototyping. The main goal when using evolutionary prototyping is to build a very robust prototype in a structured manner and constantly refine it. The reason for this approach is that the evolutionary prototype, when built, forms the heart of the new system, and the improvements and further requirements will then be built. When developing a system using evolutionary prototyping, the system is continually refined and rebuilt. "…evolutionary prototyping acknowledges that we do not understand all the requirements and builds only those that are well understood." This technique allows the development team to add features, or make changes that couldn't be conceived during the requirements and design phase. For a system to be useful, it must evolve through use in its intended operational environment. A product is never "done;" it is always maturing as the usage environment changes…we often try to define a system using our most familiar frame of reference—where we are now. We make assumptions about the way business will be conducted and the technology base on which the business will be implemented. A plan is enacted to develop the capability, and, sooner or later, something resembling the envisioned system is delivered. Evolutionary prototypes have an advantage over throwaway prototypes in that they are functional systems. Although they may not have all the features the users have planned, they may be used on an interim basis until the final system is delivered. "It is not unusual within a prototyping environment for the user to put an initial prototype to practical use while waiting for a more developed version…The user may decide that a 'flawed' system is better than no system at all." In evolutionary prototyping, developers can focus themselves to develop parts of the system that they understand