A condition hierarchy

In addition to the scoping of control, CL object system conditions are placed in a hierarchy:

 condition; 
       serious-condition; 
               error; 
                 simple-error;  
                 arithmetic-error; 
                    division-by-zero, 
                    floating-point-overflow, 
                    ...
       warning; 
        .... 
      etc;

This hierarchy can be extended by the programmer, and handlers can be bound to any tag here.