anchor.diff:      DataType:= vftString;
       Size := 255;
     end;
  +  with aFieldDefs.AddFieldDef do
  +  begin
  +    Name := aPrefix + FLD_ATTRIBUTE3;
  +    DataType:= vftString;
  +    Size := 255;
  +  end;
   end;
   
   class function TmUprightDatum.GetKeyField: String;
  
positive.code:     FValue : double;
      FAttribute1 : TNullableString;
      FAttribute2 : TNullableString;
      FEventType : TmUprightEventType;
  
      FDatumKey : String;
  
negative.code:     Result := FEvent.Attribute1.AsVariant
    else if aFieldName = FLD_ATTRIBUTE2 then
      Result := FEvent.Attribute2.AsVariant
    else if aFieldName = FLD_ATTRIBUTE3 then
      Result := FEvent.Attribute3.AsVariant
    else if aFieldName = FLD_UPRIGHT then
      Result := FUpright
    else if aFieldName = FLD_HIGHLIGHT then
  