  We present an algorithm for deriving partonic flavour labels to be applied to
truth particle jets in Monte Carlo event simulations. The inputs to this
approach are final pre-hadronization partons, to remove dependence on
unphysical details such as the order of matrix element calculation and shower
generator frame recoil treatment. These are clustered using standard jet
algorithms, modified to restrict the allowed pseudojet combinations to those in
which tracked flavour labels are consistent with QCD and QED Feynman rules. The
resulting algorithm is shown to be portable between the major families of
shower generators, and largely insensitive to many possible systematic
variations: it hence offers significant advantages over existing ad hoc
labelling schemes. However, it is shown that contamination from multi-parton
scattering simulations can disrupt the labelling results. Suggestions are made
for further extension to incorporate more detailed QCD splitting function
kinematics, robustness improvements, and potential uses for truth-level physics
object definitions and tagging.
