SDLC Model: RAD Lifecycle Model

The RAD (Rapid Application Development) model is a high speed version of the waterfall model. The emphasis is on short development cycle. Short development cycle is achieved by using component-based construction. Typical use for RAD development is for information systems.
Following are the four phases of RAD:

1. Requirements Planning:
The Requirements Planning stage consists of a review of the areas immediately associated with the proposed system. This review produces a broad definition of the system requirements in terms of the functions the system will support.
The deliverables from the Requirements Planning stage include an outline system area model (entity and process models) of the area under study, a definition of the system's scope, and a cost justification for the new system.

2. User Design:
The User Design stage consists of a detailed analysis of the business activities related to the proposed system. Key users, meeting in workshops, decompose business functions and define entity types associated with the system. They complete the analysis by creating action diagrams defining the interactions between processes and data. Following the analysis, the design of the system is outlined. System procedures are designed, and preliminary layouts of screens are developed. Prototypes of critical procedures are built and reviewed. A plan for implementing the system is prepared.

3. Construction:
In the Construction stage, a small team of developers, working directly with users, finalizes the design and builds the system. The software construction process consists of a series of "design-and-build" steps in which the users have the opportunity to fine-tune the requirements and review the resulting software implementation. This stage also includes preparing for the cutover to production.
In addition to the tested software, Construction stage deliverables include documentation and instructions necessary to operate the new application, and routines and procedures needed to put the system into operation.

4. Implementation:
The implementation stage involves implementing the new system and managing the change from the old system environment to the new one. This may include implementing bridges between existing and new systems, converting data, and training users. User acceptance is the end point of the implementation stage.