• Table of Contents

Review

For this week, we will cover the various goal modeling tools, but before doing so, we will do a quick review on the what is a goal. As a recap from the previous lecture, goals are a representation of stakeholder objectives.

• The purpose of having a goal is that it creates an objective which a system should achieve through cooperation of actors in the intended software in the environment.
• It can be classified as either functional or non-functional goals, which can be decomposed from high-level objectives to low-level requirements.

Goal modelling expresses the relationships between a system and its environment. It is useful as it clarifies requirements, enables requirement completeness, and connects requirements to design.

Goal Modeling

There are various notations for goal models used in software development.

• i* (i star) is a modeling language suitable for an early phase of system modeling in order to understand the problem domain.
• KAOS (Knowledge Acquisition in Automated Specification) is a goal-oriented software requirements capturing approach in requirements engineering.
• UML Use Case diagram is a graphical representation of the actors, use cases, and their relationships.

For both in lectures and labs, we will be using the i* notation. As an introductory, i* allows the modeling of actors' goals, tasks, and resources, and how these are related to system components. The i* goal modeling notation provides two kinds of diagram:

Figure 6.1 All elements of the i* notation.

1. Strategic Dependency (SD) Diagram: Defines relationships between roles in terms of specific goals that one role depends on the other role to provide.
2. Strategic Rationale (SR) Diagram: Analyze the goals identified on the SD model into subsidiary goals and tasks.

Another specific goal modeling method is KAOS, which provides a way of defining goals and obstacles, underpinned by a formal (mathematical) method of analysis.

Figure 6.2 Basic constructs of the KAOS framework.

The choice between i* and KAOS may depend on the specific requirements of the project.

Goal Modeling Tools