Mixins were introduced with Flavors by Howard Cannon in 1979. Flavors/Mixins were used to implement some of the early MIT Lisp Machine user interface, IO and networking code.
'aspect advice' was mostly introduced in Lisp in 1966 by Warren Teitelman: http://dspace.mit.edu/handle/1721.1/6905 See the discussion of ADVISE and a BEFORE example in the paper...
From there it came to Interlisp, Maclisp, Flavors and CLOS...
http://lispm.de/docs/Publications/Flavors/Flavors,%20a%20non...
'aspect advice' was mostly introduced in Lisp in 1966 by Warren Teitelman: http://dspace.mit.edu/handle/1721.1/6905 See the discussion of ADVISE and a BEFORE example in the paper... From there it came to Interlisp, Maclisp, Flavors and CLOS...