  The representation of units and dimensions in informatics systems is barely
codified and often ignored. For instance, the major languages used in
scientific computing (Fortran, C and Python), have no type for dimension or
unit, and so physical quantities are represented in a program by variables of
type real, resulting in the possibility of unit or dimensional errors. In view
of this danger, many authors have proposed language schemes for unit-checking
and conversion. However, since many physical quantities have the same units, it
is possible for a block of code to be unit-compatible, but still physically
meaningless. We demonstrate the limitations of three Python unit-libraries and
present a justification and method for checking kind-of-quantity.
