2.5 Summary

• The quality and productivity achieved in a software project depends on the process used for executing the project. Due to this, processes form the heart of software engineering.
• A process is the set of activities that are performed in some order so that the desired results will be achieved. A process model is a general process specification which has been found to be best suited for some situations.
• A software process consists of many different component processes, most important being the development process and the project management process.
• Development process focuses on how the software is to be engineered. There are many different process models, each being well suited for some type of problems.
• The waterfall model is conceptually the simplest model of software development, where the requirement, design, coding, and testing phases are performed in linear progression. It has been very widely used, and is suitable for well-understood problems.
• In the prototyping model, a prototype is built before building the final system, which is used to further develop the requirements leading to more stable requirements. This is useful for projects where requirements are not clear.
• In the iterative development model, software is developed in iterations, each iteration resulting in a working software system. This model does not require all requirements to be known at the start, allows feedback from earlier iterations for next ones, and reduces risk as it delivers value as the project proceeds.
• In RUP, a project is executed in a sequence of four phases—inception, elaboration, construction, and transition, each ending in a defined milestone. A phase may itself be done iteratively. The subprocesses of requirements, design, coding, testing, etc. are considered as active throughout the project, though their intensity varies from phase to phase. RUP is a flexible framework which can allow a project to follow a traditional waterfall if it wants to, or allow prototyping, if it so wishes.
• In the timeboxing model, the different iterations are of equal time duration, and are divided into equal length stages. There is a committed team for each stage of an iteration. The different iterations are then executed in a pipelined manner, with each dedicated team working on its stage but for different iterations. As multiple iterations are concurrently active, this model reduces the average completion time of each iteration and hence is useful in situations where short cycle time is highly desirable.
• Agile approaches to development are based on some key principles like developing software in small iterations, working system as the measure of progress, and allowing change at any time. In extreme programming (XP) approach, a project starts with short user stories, details of which are obtained in the iteration in which they are implemented. In an iteration, development is done by programmer-pairs, following the practices of testdriven development, frequent integration, and having simple designs which are refactored when needed.
• The project management process focuses on planning and controlling the development process and consists of three major phases—planning, monitoring and control, and termination analysis. Much of project management revolvesaround the project plan, which is produced during the planning phase.