You can create functions to define specific operations that aren’t available through built-in functions. In Process, decisions created using the Function notation return a value only when invoked from another decision.

To successfully invoke a function from another decision, the number and type of parameters in the function invocation must match those in the function definition.

The following example demonstrates a function implementation in Process. Here, the output decision invokes a function decision to calculate the seasonal discount percentage. The function decision contains the logic for regular discounts in the form of a decision table.

Description of the illustration dmn-function.png

1. Add a new decision element to the model.
   1. In graph view, click Expand next to Decision on the diagram palette. Select Function and drag it onto the canvas. Double-click the element to edit its logic. You can also edit the function's logic from the properties pane; select the element, then select Open Properties , and in the properties pane click Edit next to the Name field.
      Click Close to return to the canvas.
   2. In list view, click Add new decision in the Decisions bar and select Function from the Create Decision window.
   A function with empty Parameters and Body fields is created, with the Expression notation selected by default for the Body field.
2. In the Parameters field, click Add to add a new parameter. Enter a name for the parameter and select a data type for it. See Data Types.
3. In the Body field, click Change body to change the logical notation. Select the required notation from available options.
   
   Description of the illustration dmn-func-entry.png
   
4. Now, configure the logic for the selected notation. You can use input variables or built-in functions to define the logic.
5. Click Save to save and validate changes manually. Changes you make within the decision model are also automatically saved and validated from time to time. Errors, if any, are displayed within the decision.