SCRUM views the systems development process as a collection of actions that integrate known workable mechanisms and procedures with the best development team to develop systems. Since these actions are loose, controls to handle the process and underlying risks are used. SCRUM is a typical upgrade of the commonly utilised incremental object-oriented development cycle.
Although waterfall methodology makes it compulsory the use of undefined processes, it has a huge drawback. Its linear nature gives it this large drawback. The process does not provide way of responding to unanticipated output from any of the transitional stages.
This method is analogous to the peeling of onion layers that corresponds to users deciding whether to send prototype back to preceding phases or termination of the development process. Spiral methodology stages and stage processes are linear. Requirement analysis and design activities are conducted in requirements phase and design phase respectively with each of the stages comprising of linear, precisely and clearly communicated defined processes
This is an improvement on the Spiral method. Each of the iteration comprises of all phases in standard Waterfall model. Each of these iterations covers a single set of parsed functionality. The overall project deliverable expected is subdivided into designated subsystems, each with clean interfaces. This method allows one to test the feasibility of a subsystem and its technology in the inceptive iterations. Later iterations improve the the project while increasing the speed of delivery. This method increases flexibility, has a better cost control and checks delivery of systems. Nevertheless, the Iterative method is also linear as underlying development processes are still defined and linear. Each of the development technologies improve on another with no significant change.