🚀 go-pugleaf

The Adobe spec (5001.DSC_Spec.pdf, Version 3.0, p.35) says:

The revision field should be taken to be upwardly compatible with
  procsets of the same version number. That is, if `myprocs 1.0 0' is
  requested, then `myprocs 1.0 2' should be compatible, although the
  converse (backward compatibility) is not necessarily true. If the
                                                              ^^^^^^
  revision field is not present, a procset may be substituted as long
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  as the version numbers are equal. Different versions of a procset
  may not be upwardly compatible and should not be substituted.

This implies that the `revision' field is optional which contradicts
the definition of the procset name:

<procname> ::= <name> <version> <revision>

<name> ::=
    <version> ::= <real>
    <revision> ::= <uint>

Can someone clarify whether this is an error in the specification
or whether I'm misinterpreting something?

Werner