3.0.1a3: global classes

I was expecting classes to be global, like variables. Is it not possible to do 
what I am attempting in the commented-out statements in the following? I get a 
syntax error.

body common control
{
bundlesequence => { "month" };
}

bundle common g
{
classes:
    "month1" expression => "January";

vars:
    month1::
      "mth1" string => "January (common)";
    !month1::
      "mth1" string => "Not January";
}

bundle agent month
{
classes:
    "month2" expression => "January";

reports:
    month2::
       "January (agent)" ;
    January::
       "$(g.mth1)";

#   $(g.month1)::
#      "$(g.mth1)";
}

BTW, this reports

January (agent)
Not January

so expression (at least) still doesn't work in "bundle common".

Jim