3.2. Creating custom data types for DMN boxed expressions in Business Central

Procedure

1. In Business Central, go to Menu Design Projects, click the project name, and select the DMN file you want to modify.
2. In the DMN designer canvas, select a decision node or business knowledge model for which you want to define the data types and click the Edit icon to open the DMN boxed expression designer.

3. If the boxed expression is for a decision node that is not yet defined, click the undefined table to select the type of boxed expression you want to use, such as a boxed literal expression, boxed context expression, decision table, or other DMN boxed expression.

   図3.24 Selecting the logic type for a decision node

   

4. Click the cell for the table header, column header, or parameter field (depending on the boxed expression type) for which you want to define the data type and click Manage to go to the Data Types page where you can create a custom data type.

   図3.25 Managing data types for a column header value

   

   You can also set and manage custom data types for a specified decision node or business knowledge model node by selecting the Properties icon in the upper-right corner of the DMN designer:

   図3.26 Managing data types in decision requirements diagram (DRD) properties

   

   The data type that you define for a specified cell in a boxed expression determines the structure of the data that you use within that associated table, column, or field in the boxed expression.

   In this example, an output column Credit Score Rating for a DMN decision table defines a set of custom credit score ratings based on an applicant’s credit score.

5. On the Data Types page, click New Data Type to add a new data type or click Import Data Object to import an existing data object from your project that you want to use as a DMN data type.

   If you import a data object from your project as a DMN data type and then that object is updated, you must re-import the data object as a DMN data type to apply the changes in your DMN model.

   For this example, click New Data Type and create a Credit_Score_Rating data type as a string:

   図3.27 Adding a new data type

   

   If the data type requires a list of items, enable the List setting.

6. Click Add Constraints, select Enumeration from the drop-down options, and add the following constraints:

   • "Excellent"
   • "Good"
   • "Fair"
   • "Poor"
   • "Bad"

   図3.28 Adding constraints to the new data type

   

   To change the order of data type constraints, you can click the left end of the constraint row and drag the row as needed:

   図3.29 Dragging constraints to change constraint order

   

   For information about constraint types and syntax requirements for the specified data type, see the Decision Model and Notation specification.

7. Click OK to save the constraints and click the check mark to the right of the data type to save the data type.

8. Return to the Credit Score Rating decision table, click the Credit Score Rating column header, set the data type to this new custom data type, and define the rule values for that column with the rating constraints that you specified.

   図3.30 Decision table for credit score rating

   

   In the DMN decision model for this scenario, the Credit Score Rating decision flows into the following Loan Prequalification decision that also requires custom data types:

   図3.31 Decision table for loan prequalification

   

9. Continuing with this example, return to the Data Types window, click New Data Type, and create a Loan_Qualification data type as a Structure with no constraints.

   When you save the new structured data type, the first sub-field appears so that you can begin defining nested data fields in this parent data type. You can use these sub-fields in association with the parent structured data type in boxed expressions, such as nested column headers in decision tables or nested table parameters in context or function expressions.

   For additional sub-fields, select the addition icon next to the Loan_Qualification data type:

   図3.32 Adding a new structured data type with nested fields

   

10. For this example, under the structured Loan_Qualification data type, add a Qualification field with "Qualified" and "Not Qualified" enumeration constraints, and a Reason field with no constraints. Add also a simple Back_End_Ratio and a Front_End_Ratio data type, both with "Sufficient" and "Insufficient" enumeration constraints.

    Click the check mark to the right of each data type that you create to save your changes.

    図3.33 Adding nested data types with constraints

    

    To change the order or nesting of data types, you can click the left end of the data type row and drag the row as needed:

    図3.34 Dragging data types to change data type order or nesting

    

11. Return to the decision table and, for each column, click the column header cell, set the data type to the new corresponding custom data type, and define the rule values as needed for the column with the constraints that you specified, if applicable.

    図3.35 Decision table for loan prequalification