Object classes allow a series of actions to be performed on a group of package objects at installation or removal. You assign objects to a class in the prototype file. All package objects must be given a class, although the class of none is used by default for objects that require no special action.
The installation parameter
defined in the pkginfo file, is a list of classes to
be installed (including the none class).
CLASSES list determines
the order of installation. Class none is always installed
first, if present, and removed last. Since directories are the fundamental
support structure for all other file system objects, they should all be assigned
to the none class. Exceptions can be made, but as a general
rule, the none class is safest. The reason for this is
to ensure that the directories are created before the objects they will contain
and also to ensure that no attempt is made to delete a directory before it
has been emptied.