Ordered binary decision diagrams (OBDDs) and several more general BDD models
have turned out to be representations of Boolean functions which are useful
in applications like verification, timing analysis, test pattern generation or
The hidden weighted bit function (HWB) is of particular interest, since it
seems to be the simplest function with exponential OBDD size.
The complexity of this function with respect to different circuit models,
formulas, and various BDD models is discussed.