From: vincent@famillebelliard.fr   
      
   > note that garbage collection in multi-threaded application was proven to   
   > be possible using reference counts, even for cyclic graphs.   
      
   Yes, of course, it's possible to use references count in that case but it   
   needs extra data to search cycles and it cost a lot of CPU if you want to   
   release cycles as soon as they are not referenced anymore.   
      
   The use of qualified references avoid a lot of job even if it cost a   
   little bit more in data (because you must count references separately).   
      
   When an object has at least one reference from a local or global   
   variable, in no way it can be destroyed. In that case, when you release   
   one reference on the object you don't have extra job to do.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)