Label Propagation

The RE-Tools toolkit uses qualitative reasoning to evaluate goal achievement in Softgoal Interdependency Graphs (SIGs) based on the Label Propagation Procedure defined in this book, with an extension to support both closed-world and open-world assumptions.

The Label Propagation rules with closed-world assumptions as described in the book are illustrated here.

The extended Label Propagation rules with open-world assumptions are illustrated here.

Follow the instructions below to assign a goal achievement label of a node to trigger the automated Label Propagation Procedure to assign the goal achievement labels of its parent goal, successively upward the goal graph.

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1) Open your model. For an example, open the example model file bundled with the RE-Tools installation. See here for the instructions. Click + symbol to expand the NFR Framework model folder, the Example 2 folder. Double-click PIG1 diagram to display the diagram.
2) Right click the leaf node (“Encryption[ID/Password” in this example) to display the pull-down menu. Click Tagged Values to display the Tagged Value Editor.
3) Click the pull-down menu for the Label attribute. Click Satisficed label. A check mark will be displayed on the leaf node to represent the value.
4) Based on the Label Propagation Procedure, the parent node is evaluated to be Denied when a child node of a Break(--) contribution is Satisficed. The Denied achievement label is depicted by a cross mark.
5) In turn, based on the Open World Assumption, the parent node’s achievement label is Unknown (no label icon).

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Switching between Open-world and Closed-world assumptions

Step 1

1) Click Tools Menu.
2) Click Options. The Options dialog will be displayed.

Step 2

1) Click RE-Tools.
2) Click Label Evaluation.
3) Click the pull-down menu for World Assumption. Select ClosedWorld (or OpenWorld depending on the desirable world assumption).
4) Click OK. The labels of all model elements in the current diagram will be re-evaluated from bottom-up in the order 1-4 as shown in the diagram below.