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Guideline (Intermediate,Concept & Evaluation) Softgoals and Goals should be decomposed. Open Version
Discussion: One of the objectives of creating i* models is to show how Goals and Softgoals can be achieved through operationalization, or though more concrete actions and design decisions included in the model. This process of finding alternatives which satisfy goals and sofgoals is called “operationalizing” or decomposing elements. Therefore, modelers are encouraged to try not to leave Softgoals and Goals as leafs elements, or elements which do not have any incoming link. Figure 1 depicts one scenario where a Softgoal is left as a leaf. Figure 2 depicts a general example of when a Softgoal is considered a leaf element or a non-leaf element. Figure 4 depicts an example of Goal leaf and non-leaf elements. In cases such as this, the model is incomplete, not all of the requirements or (soft)goals contained in the model can be achieved through the alternatives included in the model. If this Softgoal leaf element is left unconnected with other model elements through Contribution Links and/or Dependency Links, it will be difficult to know whether this Softgoal (requirement) is satisficed. It may be allowable to leave Softgoals as leafs in initial, incomplete models, but later, effort should be made to find ways to achieve all Softgoals. Figure 2 illustrates connecting such a Softgoal leaf to other model elements using incoming Contribution Link(s) or Dependency Link(s) in order to show how Softgoals are achieved.
Refining and decomposing Goals and Softgoals provide the advantage of developing more complete and accurate models. More accurate models, however, might lead to more complex models, which impacts the time, effort, and cost of the design process. Therefore, the trade-off between these different aspects should be taken into consideration. It may be advisable to leave softgoals and goals as leaf elements if the model is very large, but this incompleteness should be noted and justified.
Refer to Section 5.6 ‘Leaf Elements’ for definition of leaf element.
Refer to Section 5.8 ‘Operationalizations and Refinement of Goals and Softgoals’ for more information about refining and decomposing Goals and Softgoals.
Figure 1 One possible scenario where a Softgoal is left as a model leaf
Figure 2 Two ways to avoid leaving a Softgoal as a model leaf
Figure 3 A general example of when a Softgoal is considered a leaf element or a non-leaf element
Figure 4 Scenario where Goals are leaf and non-leaf elements
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