@GenerateImpl
public interface Base extends IModelElement {
    ModelElementType TYPE = new ModelElementType(Empty.class);
}

@Type(base = Base.class, possible = { Text.class, Image.class, Pdf.class })
@XmlListBinding
(
   path = "description", 
   mappings = 
   {
       @XmlListBinding.Mapping(element = "text", type = Text.class),
       @XmlListBinding.Mapping(element = "image", type = Image.class), 
       @XmlListBinding.Mapping(element = "pdf", type = Pdf.class)
   }
)
    
ListProperty PROP_DESCRIPTION = new ListProperty(TYPE, "Description");
    
ModelElementList<Empty> getDescription();

@GenerateImpl
public interface Base extends IModelElement {
    ModelElementType TYPE = new ModelElementType(Base.class);
    
    // *** Content ***
    ValueProperty PROP_CONTENT = new ValueProperty(TYPE, "Content");
    Value<String> getContent();
    void setContent(String value);
}

@GenerateImpl
public interface Image extends Base {
    ModelElementType TYPE = new ModelElementType(Image.class);

    // *** Title ***

    @XmlBinding(path = "title")
    @Label(standard = "Title")
    @Required
    ValueProperty PROP_CONTENT = new ValueProperty(TYPE, Base.PROP_CONTENT);
}