A plurality of measured product ion spectra are produced using a DIA tandem mass spectrometry method. One or more product ions are retrieved from a spectral library of known compounds or one or more theoretical product ions are calculated for the known compounds of a database. The one or more product ions or one or more theoretical product ions for each known compound are compared to the measured product ion spectra to identify one or more known compounds in the sample. A database of related known compounds is searched using one or more known compounds, producing one or more matching related compounds and one or more product ions for each related compound. The one or more product ions for each related compound are compared to the measured product ion spectra to identify one or more related compounds in the sample.