Chapter 3. Decision Model and Notation (DMN)

Procedure

1. On the traffic-violation project’s home page, click Add Asset.

2. On the Add Asset page, click DMN. The Create new DMN window is opened.

   1. In the Create new DMN window, enter Traffic Violation in the DMN name field.
   2. From the Package list, select com.myspace.traffic_violation.
   3. Click Ok. The DMN asset in the DMN designer is opened.
3. In the DMN designer canvas, drag two DMN Input Data input nodes on to the canvas.
4. Double-click each input node and rename one to Driver and the other to Violation.
5. Drag a DMN Decision decision node on to the canvas.
6. Double-click the decision node and rename it to Fine.

7. Click the Violation input node, select the Create DMN Information Requirement icon and click the Fine decision node to link the two nodes.

   Figure 3.2. Create DMN Information Requirement icon

   
8. Drag a DMN Decision decision node on to the canvas.
9. Double-click the decision node and rename it to Should the driver be suspended?.
10. Click the Driver input node, select the Create DMN Information Requirement icon and click the Should the driver be suspended? decision node to link the two nodes.
11. Click the Fine decision node, select the Create DMN Information Requirement icon, and select the Should the driver be suspended? decision node.

12. Click Save.

    Note

    As you periodically save a DRD, the DMN designer performs a static validation of the DMN model and might produce error messages until the model is defined completely. After you finish defining the DMN model completely, if any errors remain, troubleshoot the specified problems accordingly.

Procedure

1. To create the tDriver custom data type, click Add on the Data Types tab, enter tDriver in the Name field, and select Structure from the Type list.

2. Click the check mark to the right of the new data type to save your changes.

   Figure 3.4. The tDriver custom data type

   

3. Add each of the following nested data types to the tDriver structured data type by clicking the plus sign next to tDriver for each new nested data type. Click the check mark to the right of each new data type to save your changes.

   • Name (string)
   • Age (number)
   • State (string)
   • City (string)
   • Points (number)
4. To create the tViolation custom data type, click Add on the Data Types tab, enter tViolation in the Name field, and select Structure from the Type list.

5. Click the check mark to the right of the new data type to save your changes.

   Figure 3.5. The tViolation custom data type

   

6. Add each of the following nested data types to the tViolation structured data type by clicking the plus sign next to tViolation for each new nested data type. Click the check mark to the right of each new data type to save your changes.

   • Code (string)
   • Date (date)
   • Type (string)
   • Speed Limit (number)
   • Actual Speed (number)

7. To add the following constraints to the Type nested data type, click the edit icon, click Add Constraints, and select Enumeration from the Select constraint type pull-down menu.

   • speed
   • parking
   • driving under the influence
8. Click OK, then click the check mark to the right of the Type data type to save your changes.

9. To create the tFine custom data type, click Add on the Data Types tab, enter tFine in the Name field, select Structure from the Type list, and click Save.

   Figure 3.6. The tFine custom data type

   

10. Add each of the following nested data types to the tFine structured data type by clicking the plus sign next to tFine for each new nested data type. Click the check mark to the right of each new data type to save your changes.

    • Amount (number)
    • Points (number)
11. Click Save.

Procedure

1. Click the Model tab on the DMN designer and click Properties icon in the upper-right corner of the DMN designer to expose the DRD properties.
2. In the DRD, select the Driver input data node and in the Properties panel, select tDriver from the Data type pull-down menu.
3. Select the Violation input data node and select tViolation from the Data type pull-down menu.
4. Select the Fine input data node and select tFine from the Data type pull-down menu.

5. Select the Should the driver be suspended? decision node and set the following properties:

   • Data type: string
   • Question: Should the driver be suspended due to points on his driver license?
   • Allowed Answers: Yes,No
6. Click Save.

Procedure

1. To calculate the fine, in the DMN designer canvas, select the Fine decision node and click the Edit icon to open the DMN boxed expression designer.
2. Click Select expression Decision Table.
3. For the Violation.Date, Violation.Code, and Violation.Speed Limit parameter fields, right-click and select Delete for each field.
4. Click the Violation.Actual Speed column header and enter the expression Violation.Actual Speed - Violation.Speed Limit in the Name field.
5. Right-click the Fine parameter field and select either Insert left or Insert right.
6. Click the output-2 column sub-header, enter Amount in the Name field, and select number from the Data Type pull-down menu.
7. Similarly, click the output-1 column sub-header, enter Points in the Name field, and select number from the Data Type field.

8. Next, enter the following values in the first row of the decision table:

   • Violation.Type: "speed"
   • Violation.Actual Speed - Violation.Speed Limit: [10..30)
   • Amount: 500

   • Points: 3

     Right-click the first row and select Insert below to add another row.

9. Enter the following values in the second row of the decision table:

   • Violation.Type: "speed"
   • Violation.Actual Speed - Violation.Speed Limit: >= 30
   • Amount: 1000

   • Points: 7

     Right-click the second row and select Insert below to add another row.

10. Enter the following values in the third row of the decision table:

    • Violation.Type: "parking"
    • Violation.Actual Speed - Violation.Speed Limit: -
    • Amount: 100

    • Points: 1

      Right-click the third row and select Insert below to add another row.

11. Enter the following values in the fourth row of the decision table:

    • Violation.Type: "driving under the influence"
    • Violation.Actual Speed - Violation.Speed Limit: -
    • Amount: 1000
    • Points: 5
12. Click Save.
13. To define the driver suspension rule, return to the DMN designer canvas, select the Should the driver be suspended? decision node, and click the Edit icon to open the DMN boxed expression designer.
14. Click Select expression Context.
15. Click ContextEntry-1, enter Total Points as the Name, and select number from the Data Type pull-down menu.
16. Click the cell next to Total Points, select Literal expression from the context menu, and enter Driver.Points + Fine.Points as the expression.
17. In the cell below Driver.Points + Fine.Points, select Literal Expression from the context menu, and enter if Total Points >= 20 then "Yes" else "No".

18. Click Save.

    You have defined how to calculate the fine and the context for deciding when to suspend the driver. You can navigate to the traffic-violation project page and click Build to build the example project and address any errors noted in the Alerts panel.