This stable version of the Guideline Wiki Page displays the guideline as per the i* Style of the University of Toronto. Registered users can use 'Open Version' link right at the end of the guideline statement below to access the open version of this page
Guideline (Beginner,Concept) To indicate that a Goal can be achieved by performing several sub-tasks, model the decomposition by introducing a Task. Open Version
Discussion: Use a single Means-Ends Link to connect a Task to a Goal, then, decompose this Task into sub Tasks using Decomposition Links. In the example, the Task “Provide health service” is decomposed into the all the sub-tasks below it. Also, these sub Tasks can be decomposed further, if required based on the nature and context of the analysis, into more sub Goals, Softgoals, Tasks, and Resources.
Figure 1 depicts a correct scenario of a Goal decomposition by introducing a Task. Figures 2 and 3 illustrate incorrect scenarios where the main goal is incorrectly and directly decomposed using Decomposition and Contribution Links.
Note: See the guideline, “Don’t mix Goals and Tasks in the Means-Ends links” for further discussion about Goal decomposition and a note about the difference between i* and Tropos in decomposing Goals into sub-goals.
Figure 1 A correct scenario of a Goal decomposition by introducing a Task
Figure 2 A wrong scenario where the goal is incorrectly and directly decomposed using Decomposition Links
Figure 3 A wrong scenario where the goal is incorrectly and directly decomposed using Contribution Links
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