private Field createField(SelectionEvent<Integer> selectionEvent) {
if (selectionEvent.getSelectedItem() == FieldData.TYPE_FACT) {
return new FactAssignmentField(field.getName(), helper.getFieldType());
} else {
if (selectionEvent.getSelectedItem() == FieldData.TYPE_COLLECTION) {
CollectionFieldData collectionFieldData = new CollectionFieldData();
collectionFieldData.setName(field.getName());
return collectionFieldData;
} else {
FieldData fieldData = new FieldData(field.getName(), "");
fieldData.setNature(selectionEvent.getSelectedItem());
return fieldData;