The Scrum lifecycle is composed of four phases: Planning, Staging, Development, and Release. The following example illustrates a Scrum project and the lifecycle: Jeff Sutherland, one of the Scrum founders, serves at an organization that applies Scrum to build a hand-held medical system. Their evolutionary delivery release cycle is three months, composed of three Scrum Sprints (iterations). As this is a relatively mature and ongoing project, the vision-oriented Planning phase is bypassed (its goals having already been satisfied), and each release begins with Staging addition and prioritization of items to work on in the first of the three Sprints. During the prior three-month release cycle, some subject matter experts were involved in enough requirements analysis to kick-start the release. In collaboration with the architect and some other team members, the new items are assigned tentative estimates, with no item larger than three person-days of effort. Staging is followed by three iterations of the Development phase. Quality assurance (QA) occurs in each, but the third Sprint has a special focus on QA, with less new development.