Goal Modeling - Principles

Principles

Goals are objectives which a system should achieve through cooperation of actors in the intended software and in the environment. Goal modeling is especially useful in the early phases of a project. Projects may consider how the intended system meets organizational goals, why the system is needed and how the stakeholders’ interests may be addressed.

A goal model:

• Expresses the relationships between a system and its environment (i.e. not only on what the system is supposed to do, but why). The understanding this gives, of the reasons why a system is needed, in its context, is useful because "systems are increasingly used to fundamentally change business processes rather than to automate long-established practices".

• Clarifies requirements : Specifying goals leads to asking "why", "how" and "how else". Stakeholders' requirements are often revealed in this process, with less risk of either missing requirements, or of over-specifying (asking for things that are not needed).

• Allows large goals to be analyzed into small, realizable goals:

• Deals with conflicts : goal modeling can identify and help to resolve tradeoffs between cost, performance, flexibility, security and other goals. Goal modeling can also reveal divergent interests between stakeholders. Goal modeling can identify conflicts because meeting one goal can interfere with meeting other goals.

• Enables requirement completeness to be measured: Requirements can be considered complete if they fulfil all the goals in the goal model.

• Connects requirements to design: for example, the i* "Non-Functional Requirements (NFR) framework" uses goals to guide the design process.