Create Decision Tables

Decision tables are the notation of choice to model complex logic. Their tabular layout helps you effectively document all the possible conditions and results of a problem.

To create a decision table:

1. On the Diagram palette, under Decisions select Decision Table and drag it onto the canvas.
2. Double-click the element to edit its logic.
   You can also edit the table's logic from the Decision Properties pane. Click the three dots on the element and select Edit to open the Decision Properties pane of the element. Click Edit next to the Name field to edit the element.
3. Click Close to return to the canvas.

Learn about each decision table element in detail in the following topics:

• Define Decision Table Input
• Define Decision Table Output
• Configure Rules
• Configure a Hit Policy

The following figure shows an example decision table with all its elements noted:

Description of the illustration dmn-dt-callouts.png

1. Row and column controls – Add or remove rows and columns
2. Input Expression cell – Contains the expression associated with a particular input column or clause.
3. Hit Policy Indicator cell – Displays the hit policy selected for the table.
4. Rules – Rows within the table.
5. Input Entry cell – Contains an input entry.
6. Output Entry cell – Contains an output entry.
7. Output Label cell – Contains the name of the decision.
8. Add Annotation button – Adds a column for documenting or annotating decision rules. Annotations aren’t considered as part of the decision logic; they serve as explanatory notes for designers.
9. Cut, Copy, and Paste button – Cut, copy, and paste rows and columns within decision tables. However, you cannot use this functionality to:
   • Copy a row into a column, and vice versa.
   • Copy an input column into an output column or an annotation column, and vice versa.
10. Table Actions - Copy and paste a decision table.

Note that when you edit a decision table, the total number of resultant errors and warnings are displayed on the top-right side area above the decision table. Click the error or warning to view more details. Additionally, you can also see where the errors or warnings occur in the decision table cells.

The following image shows the errors and warnings that are displayed when you create an empty decision table:

Description of the illustration dmn-dt-errors-callout.png

1. The total count of errors and the total count of warnings.
2. Details of the errors and warnings that are displayed when you click the errors and warning counts.
3. The upper-right corner of a cell is marked in red color to indicate erroneous cells.
4. The error message appears when you hover the mouse on the red marked upper-right corner.