Create a Model

To create a new DMN model from scratch, you have to create an empty DMN model instance with the following method:

DmnModelInstance modelInstance = Dmn.createEmptyModel();

The next step is to create a DMN definitions element. Set the target namespace on it and add it to the newly created empty model instance.

 Definitions definitions = modelInstance.newInstance(Definitions.class);

Usually you want to add a decision to your model. This follows the same 3 steps as the creation of the DMN definitions element:

  1. Create a new instance of the DMN element
  2. Set attributes and child elements of the element instance
  3. Add the newly created element instance to the corresponding parent element
Decision decision = modelInstance.newInstance(Decision.class);

To simplify this repeating procedure, you can use a helper method like this one:

protected <T extends DmnModelElementInstance> T createElement(DmnModelElementInstance parentElement, String id, Class<T> elementClass) {
  T element = modelInstance.newInstance(elementClass);
  element.setAttributeValue("id", id, true);
  return element;

Validate the model against the DMN 1.3 specification and convert it to an XML string or save it to a file or stream.

DMN 1.3 diagram

The resulting XML string will reference the DMN 1.3 specification.

// validate the model

// convert to string
String xmlString = Dmn.convertToString(modelInstance);

// write to output stream
OutputStream outputStream = new OutputStream(...);
Dmn.writeModelToStream(outputStream, modelInstance);

// write to file
File file = new File(...);
Dmn.writeModelToFile(file, modelInstance);

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