An example of a Bayesian network used as a generative model in MSBayesPro. Three layers are provided reflecting the LC-MS/MS experiment in which proteins are first digested into peptides which are then matched to the MS/MS spectra. The numbers associated with the directed edges indicate peptide detectabilities (between the first two layers) and PSM identification scores (between the last two layers). Note that some peptides may not be matched with any spectra while some others may be matched with more than one spectrum. The peptides not matched to any spectra are shown using dashed lines.