anchor.diff:    { TAbstractNullable }
   
     TAbstractNullable = class abstract
  -  protected
  +  strict private
       FTagChanged: Boolean;
       FIsNull: Boolean;
  +  protected
       function GetNotNull: Boolean;
  +    function GetTagChanged: Boolean; virtual;
  +    procedure SetTagChanged (aValue : Boolean); virtual;
  +    function GetIsNull : Boolean; virtual;
  +    procedure SetIsNull(aValue : Boolean); virtual;
     public
       constructor Create(); virtual;
       function AsVariant: Variant; virtual; abstract;
  
positive.code:     function CheckIfDifferentAndAssign(const aValue : Variant) : boolean; virtual; abstract;
      function AsString: String; virtual; abstract;
  
      property IsNull: Boolean read FIsNull write FIsNull;
      property NotNull: Boolean read GetNotNull;
      property TagChanged: Boolean read FTagChanged;
    end;
  
    { TNullablesList }
  
negative.code:     function AlmostOneChanged: boolean;
      procedure Add(const aNullableItem: TAbstractNullable);
    end;
  
    TNullableDataType = (tnDateTime, tnString, tnDouble, tnInteger, tnBoolean);
  
    TNullableDateTime = class;
    TNullableString = class;
  