An addition operation adds new model objects to an existing parent object in the model. This is useful when a model variation needs to introduce new elements that are not present in the original model.

When executed, each child object is added to the parent by finding the appropriate containment feature based on the child type. If the parent has a list-valued containment, the child is appended to the list. If the parent has a single-valued containment, the child is set directly.

Validation checks that the parent is set, that children are not empty, and that each child is a valid child type for the selected parent.