anchor.diff:    Result := BoolToStr(FKey.Value, true);
   end;
   
  -procedure TBooleanDatum.SetPropertyByFieldName(const aFieldName: String; const aValue: Variant);
  -begin
  -  // none
  -end;
  -
   end.
  
positive.code:     class procedure FillVirtualFieldDefs (aFieldDefs : TmVirtualFieldDefs; const aPrefix : String);
      class function GetKeyField : String;
      function GetPropertyByFieldName(const aFieldName : String) : Variant;
      procedure SetPropertyByFieldName(const aFieldName: String; const aValue : Variant);
  
      property Key : TBooleanDatumKey read FKey;
    end;
  
negative.code: interface
  
  uses
    Classes,
    {$IFNDEF FPC}mInterfaces,{$ENDIF}
    mDataProviderFieldDefs, mDataProviderInterfaces, mDataProvider;
  
  type
  