Hi Juan,

thanks for telling me about the optimizations in Model and ActiveModel; I 
guess I should have looked more thoroughly at which classes reimplement parts 
of the mechanisms. I will add a paragraph to the implementation notes.

> - MorphicEvents are really something really different... They are not
> message sends, but [...] stateful objects that are sent around until
> handled.
OK, I see your point. They do, however, fulfill the criterion of "signaling an 
asynchronous state change" (the user pressed a key, etc.). Don't you think 
that they should at least get mentioned? 

> - You forgot the AbstractEvent hierarchy. While this is not as general
> as #when:send:to: and #changed/#update, it is closer to them than
> MorphicEvents are. AbstractEvent is used to notify various Smalltalk
> tools of system changes.
Concerning the AbstractEvent hierarchy: I do not know why I had not found this 
one, but you are of course right, it deserves some paragraphs in the text. 
Furthemore, Torsten Bergmann noted that Pharo additionally includes the 
Announcements framework. So two more event mechanisms to choose from. :-)

Thank you very much for your comments. The next draft will certainly benefit 
from them. Also thank you for your work on Cuis.

Cheers,
Peter