We then asked more precise questions of comparison, once again in interactive sessions, in order to decide on the form of the function k and its parameters. We used comparison questions similar to the ones above but with precise values, such as the following. Assume that a given ion i 1 has match score given by GNPS of 0.7, by Sirius of We acknowledge that other choices would have been possible and defer a full axiomatic analysis (determining a set of mathematical properties that only our class of functions satisfy) to future work.