Hi Edi, I looked at flexi-streams' stream.lisp some time ago, and there seems to be a lot of boilerplate code to combine various mixins to specific stream classes. Then, there seems to be code for parsing and combining what basically amounts to mixin designators, which are then again mapped on the specific stream classes. The underlying issue is not new. AMOP describes a nice way around it which creates classes composed from several mixins programmatically. About a year or so ago, Christophe Rhodes fixed SBCL so that it accepts generalized class names. The support code is little, you can find it here (usage example at the end of this mail): http://www.foldr.org/~michaelw/lisp/amop-programmatic-class.lisp I can't tell how well this is supported in Lispworks and other implementations, but it might be worth opening trouble tickets if it's not. :) OTOH, I understand the cost that comes with maintaining special-cased code for non-supporting implementations. It might not be worth it. Still, I felt like sharing this, before I forget again. :) Cheers, Michael ;;; Example code: (progn (defclass shape () ()) (defclass circle (shape) ()) (defclass color () ()) (defclass orange (color) ()) (defclass mangenta (color) ()) (defclass label-type () ()) (defclass top-labeled (label-type) ()) (defclass bottom-labeled (label-type) ())) #|| ===> (class-direct-subclasses (find-class 'circle)) () ===> (defparameter *i1* (make-programmatic-instance '(circle orange top-labeled))) ===> (defparameter *i2* (make-programmatic-instance '(circle mangenta bottom-labeled))) ===> (defparameter *i3* (make-programmatic-instance '(circle orange top-labeled))) ===> (class-direct-subclasses (find-class 'circle)) (#<Standard-Class (CIRCLE MAGENTA BOTTOM-LABELED) > #<Standard-Class (CIRCLE ORANGE TOP-LABELED) >) ||#