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.
Why are goals important?
Goals are the best way to elicit the requirements for your system. They express what a stakeholder wants – sounds simple, doesn’t it? In practice, it isn’t, because knowing your stakeholders goals is the only way to find out what he or she expects from a system, and what to develop.
The success of a project can be ascertained by looking at whether or not the goals were achieved. That means that the goals are not just signposts at the beginning of a project but they offer orientation throughout the undertaking as well as at the end, when a product has been created, a solution has been found or a service rendered. The achievement of the goals and the communication with stakeholders about them is an important part of taking advantage of its benefits.