The reference for the timing can be the time in respect of another Operation, the time in respect of a growth stage, or the time in respect of the moment when a certain temperature sum is reached. Remark 2. When Relative Timing can be associated with other PropertyValues of the PropertyVariables GrowthStage and/or TemperatureSum, then an association should be considered instead of the construction with attributes. This is not that difficult as PropertyValue can indicate a minimum and a maximum value by the PropertyValueCharacteristic.