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Fundamental to creating Decision Models is the definition of the structure of data items used within the model. An ItemDefinition is used to define the structure of the input data and, optionally, to restrict the range of allowable values of the data.  ItemDefinitions can range from a simple single type through to a complex structured type.


ItemDefinition elements are created by dragging a icon from the DMN Toolbox page onto a DMN diagram.

The core properties of an ItemDefinition element are accessed via the DMN Expression window.


To open the DMN Expression window for an ItemDefinition Element:


Simulate > Decision Analysis > DMN > DMN Expression, then select or create an ItemDefinition


Double-click on a DMN ItemDefinition

DMN Expression and Data set

This image is an overview of the DMN Expression window, showing a complex data item and the layout of the key fields used in the definition of the data.  Included is a view of a Data Set defined using this ItemDefinition.  A Data Set is an 'instance' of data conforming to an ItemDefinition, which contains a set of values to be used in the DMN simulation.

As ItemDefinitions are foundation elements in the model, it is recommended that they are validated before going on to use them in the model. This will ensure that any issues are resolved early on in the process of creating a complex model.

For more details on setting up ItemDefinitions, see these Help topics:

  • DMN Item Definition, Data Set and Input Data
  • Types of Component
  • ItemDefinition Allowed Value
  • DMN Expression Auto Completion
  • DMN Expression Validation

Learn more