Example: In the logistics domain, there are several different objects that need to be handled. The most basic, abstract element is a Shipment. Apart from the individual manifestations, each shipment has a receiver, a sender and flag indicating if it already was delivered. In addition, there are the various actual shipment elements such as Letters or Parcels. They share the attributes of a shipment, but also have their own specific characteristics: a letter has information about the used stamp, whereas parcels have an assigned weight and dimensions. This hierarchy could be further extended by an InternationalParcel, that takes all of Parcel's attributes and adds an attribute for customs information.