Ok, so my thoughts are.

1.  Whenever I see a get_* or set_* method in Ruby, I immediately get red flags.  There is almost always a better name.  .query is ok, but I'd be fine with .info.  Need to think about this more.
2.  Depending on what this class' purpose is, would give the names.  If it is a class to deal with raw package files, then the base class should Package, with Rpm and Deb as subclasses.  If it is a class to deal with package managers, then the base class should be PackageManager, with Yum and Apt as subclasses.  Either way, if we take advantage of the subclassing, then there is not need for this delegator method, since each subclass will just define the method in question.