proper way to distinguish epel from fedora

[Farkas Levente]

hi,
what's the proper way to distinguish epel from fedora in the spec file?
i'd like to add
ExcludeArch:    ppc ppc64
on epel but not in case of fedora in a package (since there is no java
on ppc on epel). but what's the current recommended way to do so?
unfortunately %{?rhel} is not defined even in rhel-5 so what else can i
use to distinguish it from fedora?
thanks in advance.

ps. anyway it'd be useful to put into the epel packaging guidelines.

-- 
  Levente                               "Si vis pacem para bellum!"