The Product Owner manages the requirements in the development and is the voice of the customer. He has the last word as to which features should be developed. Through him, the customer is involved in the entire development process. The Product Owner should be available during the entire development process because only then can the customer’s requirements flow flexibly into the development. Unlike XP, changes may only be incorporated by him at certain times.
Ideally, the Development Team consists of six plus or minus three people. It organizes itself and independently develops the software in so-called Sprints – the term for iterations in Scrum.
The term “Scrum Team” means the Product Owner, Development Team and Scrum Master as a whole.
Should a development require significantly more than nine people, Scrum does not allow for an enlargement of the Team as this would jeopardize the ability to communicate. In such a case, “Scrum of Scrums” is used: A number of Scrum Teams are formed and one or two people from each of these teams form a Team at a higher hierarchical level who also run through the Scrum process, and primarily has coordinating and integration tasks. This concept can be continued to additional levels if necessary and results in a tree structure of teams.
The Scrum Master has the task of maintaining the values and rules during the project and removing obstacles. He is also the interface between the Team and the outside world and is responsible for communication with non-team members in order to relieve the Team of this task and to act as a central point of contact.
On principle, the Scrum Master is not placed higher than the Team.
In addition there are further roles which are not part of the actual Scrum process, but have an impact on it. The following groups should also comment on the results of the Sprints in the “Review Meetings”: