Abstract superclass for domain model classes in this package.
All business objects are PLOJOs (plain old java objects) with public
constructors without parameters and simple properties implemented using
the java beans pattern (getter + setter).
This is important insofar as Mandarax ZKB by default uses built-in serialization mechanisms
to store objects (e.g., objects may occur in constant terms in certain rules). Java XML serialization
works best for PLOJOs. For similar reasons, this class implements Serializable, although the storage
mechanism used in this example does not use binary serialization.
author: Jens Dietrich version: 3.4 <7 March 05> since: 1.2