Ensure annotation factory method set correctly the data field
With the use of the latest default value plugin, the data field of an annotation (which is requried according to the model XSD) cannot be null. By default the generated class set it to an empty Object. However, this empty object let the marshaller fail when trying to convert any Resource with empty annotation (since that Object cannot be converted to a DOM Node/Element).
To improve the factory methods in charge of creating PieceOfKnowledge or Annotation should ensure that this field is not the empty Object, by an empty element.