Annotation Type PlanningId
Specifies that a bean property (or a field) is the id to match
 when 
locating
 an externalObject (often from another Thread or JVM).
 Used during Move rebasing and in a ProblemChange.
 
 It is specified on a getter of a java bean property (or directly on a field) of a PlanningEntity class,
 planning value class or any problem fact class.
 
 The return type can be any Comparable type which overrides Object.equals(Object) and
 Object.hashCode(), and is usually Long or String.
 It must never return a null instance.