Class User.A Extends %Persistent [ ClassType = persistent, ProcedureBlock ]
{
Property F As %String;
}

Class User.B Extends %Persistent [ ClassType = persistent ]
{
Property C As User.A;
}

Class User.AA Extends (%Library.Persistent, User.A) [ ClassType = persistent, ProcedureBlock ]
{

}

Class User.BB Extends (%Library.Persistent, User.B) [ ClassType = persistent ]
{
Property C As User.AA;
}