we take as a self evident foundational principle that the set of effects
to be considered as contributing to local station displacements and the
conventional models to be applied for their compensation should be
guided by rational and well considered bases, and should not be developed.
haphazardly or randomly.  for historical reasons and general consistency,
it might be prudent to retain some past practices even if they are not
fully consistent with the adopted principles; but future expansions
should be determined by specified rules!  this position paper proposes
such a set of guidelines and rationales for iers conventions updates.