The central panel of Figure lists the mzPAF-supported ion types, including the customary abcxyz designations, 'm' for internal fragmentation ions, '?' for unidentified ions, 'p' for precursor-related ions, 'I' for immonium ions, 'r' for reference ions (such as isobaric labeling related ions), 'f' for arbitrary chemical formulas, 's' for SMILES strings, and '_' for named compounds. Examples of each of these ion types are also provided.