![]() The Martin method was tailored toward knowledge intensive and UI intensive business systems. It is important to distinguish between RAD as a general alternative to the waterfall model and RAD as the specific method created by Martin. This has resulted in some confusion over the term RAD even among IT professionals. Starting with the ideas of Barry Boehm and others, James Martin developed the rapid application development approach during the 1980s at IBM and finally formalized it by publishing a book in 1991, Rapid Application Development. The advantage of this besides the two advantages above was that the users could get useful business functionality much earlier in the process. One approach used in some RAD methods was to build the system as a series of prototypes that evolve from minimal functionality to moderately useful to the final completed system. Prototypes can be usable and can evolve into the completed product.In general most users give much more useful feedback when they can experience a prototype of the running system rather than abstractly define what that system should be. In the waterfall model it was common for a user to sign off on a set of requirements but then when presented with an implemented system to suddenly realize that a given design lacked some critical features or was too complex. Users are better at using and reacting than at creating specifications.The earlier a problem can be found the cheaper it is to address. This benefit of finding problems earlier in the life-cycle rather than later was a key benefit of the RAD approach. This can provide valuable information as to the feasibility of a design and can prevent the team from pursuing solutions that turn out to be too complex or time-consuming to implement. ![]() A prototype could test some of the most difficult potential parts of the system early on in the life-cycle. Prototypes had several advantages over traditional specifications: Boehm and other subsequent RAD approaches emphasized developing prototypes as well as or instead of rigorous design specifications. The first such RAD alternative was developed by Barry Boehm and was known as the spiral model. RAD approaches, on the other hand, recognize that software development is a knowledge intensive process and provide flexible processes that help take advantage of knowledge gained during the project to improve or adapt the solution. Plan-driven approaches attempt to rigidly define the requirements, the solution, and the plan to implement it, and have a process that discourages changes. As a result, knowledge gained from the development process itself can feed back to the requirements and design of the solution. Software can radically change the entire process used to solve a problem. ![]() ![]() Software is an inherently different kind of artifact. ![]() One of the problems with these methods is that they were based on a traditional engineering model used to design and build things like bridges and buildings. Rapid application development was a response to plan-driven waterfall processes, developed in the 1970s and 1980s, such as the Structured Systems Analysis and Design Method (SSADM). Other approaches to rapid development include the adaptive, agile, spiral, and unified models. Graphical user interface builders are often called rapid application development tools. RAD is especially well suited for (although not limited to) developing software that is driven by user interface requirements. Prototypes are often used in addition to or sometimes even instead of design specifications. In general, RAD approaches to software development put less emphasis on planning and more emphasis on an adaptive process. Rapid application development ( RAD), also called rapid application building ( RAB), is both a general term for adaptive software development approaches, and the name for James Martin's method of rapid development. ![]()
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