The advantage of including an "undefined" class for taste prediction is that FART is capable of flagging tasteless molecules as well as compounds that are plausibly outside the domain of application, i.e. molecular structures that are too distinct from the train set to allow for meaningful predictions. For example, instead of forcing sodium chloride erroneously into one of the four taste labels that we have collected data on, FART classifies it as undefined. Similarly, FART classifies saturated alkanes, which are not water-soluble, as undefined as well.