Rational Unified Process. An iterative, architecture-centric, software engineering process developed by IBM Rational by incorporating the software engineering best practices. It establishes four phases of development, each of which is organized into a number of separate iterations that must satisfy defined criteria before the next phase is undertaken. In the inception phase, developers define the scope of the project and its business case. In the elaboration phase, developers analyze the project's needs in greater detail and define its architectural foundation. In the construction phase, developers create the application design and source code, and in the transition phase, developers deliver the system to users.