An attribute holder is an object that holds a list of attributes. Each of the attributes maintained by a holder are described by an Attribute object, wich is able to pickle/unpickle its value, provides the status of the attribute (eg mandatory, editable, etc), etc.
Given this, an attribute holder is able to pickle its state (made of its attribute values), and unpickle it to any DataOutputStream (resp. DataInputStream).
@see Attribute
@see Resource