anchor.diff:        class function CreateNew(): TNullableUnicodeString; overload;
   
         procedure Assign(aSource : TNullableUnicodeString); overload;
  -      procedure Assign(aSourceField : TField); overload;
  +      procedure Assign(aSourceField : TField); override; overload;
  +      procedure Assign (const aValue : String; const aBlankStringMeansNull : boolean); override; overload;
         function AsVariant: Variant; override;
   
         property Value : UnicodeString read GetValue write SetValue;
  
positive.code:     class function CreateNew(): TNullableBoolean; overload;
  
      procedure Assign(aSource : TNullableBoolean); overload;
      procedure Assign(aSourceField : TField); overload;
      function AsVariant: Variant; override;
  
      property Value : Boolean read GetValue write SetValue;
  
negative.code:       class function CreateNew() : TNullableDateTime; overload;
  
        procedure Assign(aSource : TNullableDateTime); overload;
        procedure Assign(aSourceField : TField); override; overload;
        procedure Assign (const aValue : String; const aBlankStringMeansNull : boolean); override; overload;
        function AsVariant: Variant; override;
  
        function AsString (aShowTime : boolean) : String;
  