anchor.diff:  begin
     TBooleanDatum.FillVirtualFieldDefs(aFieldDefs, aPrefix);
   end;
  +
   
   { TBooleanDatum }
   
  
positive.code: function TBooleanDatumKey.AsString: string;
  begin
    Result := BoolToStr(FValue, true);
  end;
  
  { TBooleanDataProvider }
  
negative.code:     property Key : TBooleanDatumKey read FKey;
    end;
  
    TBooleanDataProvider = class (TmDatasetDataProvider)
    strict private
      FTrueValue : TBooleanDatum;
  