The fingerprint is then used to search for matches in structural libraries. Within the SiriusAdapter step of UmetaFlow, the user can provide both the mzML and the corresponding pre-processed feature and adduct information (featureXML) as input files to SIRIUS. The algorithm then creates a .ms temporary file (SIRIUS internal format) that is used as an input for the SIRIUS executable, allowing SIRIUS to compute only the MS 2 spectra that are allocated to a feature, instead of all MS 2 data. The pre-processed or re-quantified feature matrix is then annotated with the highest ranked predictions from both algorithms using unique feature identifications (Figure ), classified as metabolite annotations level 3, according to the Metabolomics Standard Initiative nomenclature (MSI level 3) .