The Goal Diagram. The basis for good requirements.
A goal diagram is a graphic representation of goals, the relationships among stakeholders and among goals themselves.
Stakeholders: people who, for example are interested in a new solution or pursue goals. The weighting is an expression of how important a goal is to a particular stakeholder.
Goal diagrams are also described as AND/OR graphics. An AND connection elaborates on the various other sub-goals that need to be achieved to make the larger goals possible.
Conflicts can arise between two goals when they contradict each other in part or in full. Recognizing these as early as possible is an important aim of goal diagrams.
OR connections: when one goal has sub-goals, only one of which needs to be achieved to make the larger goal possible.
What are goals?
Stakeholders have objectives. They want a planned or existing system to help them achieve these objectives. Consequently, a system has to possess certain characteristics and functionalities. The description of such a charateristic or functionality (also called feature) on the basis of stakeholder objectives is what we call a goal. Klaus Pohl summed it up briefly and concisely in his book Requirements Engineering – Grundlagen Prinzipien, Techniken:
A goal is the intentional description of a characteristic feature of a system to be developed, or of its accompanying development process.