How to test object hierarchy

[favierp@sofreavia.fr (Pierre Favier)]

I am wondering how to test for two objects which types both derive from a
common root type if one of them derives from the other. In short, I am trying
to run something like the following code which does not compile because
the Class attribute applies to types or subtypes but not to objects:

   procedure Test_Hierarchy (Obj1 : in Root_Object'Class;
                             Obj2 : in Root_Object'Class) is
   begin

      if Obj1 in Obj2'Class then

         -- Do something

      else

         -- Do something else

      end if;

   end Test_Hierarchy;

Any suggestions on how to achieve the intended effect?