olemus
olemasoleva klassi (ülemklassi) omadustega uue klassi moodustamine mõnede muudatustega
= defining a new class that has the properties of an old class (the "superclass") with some changes

ülevaateid
http://rmod-pharo-mooc.lille.inria.fr/AdvancedDesignMooc/Slides/M10-2-Principles-09-SubtypingVsSubclassing.pdf

https://www2.it.uu.se/workshop/nool16/nool16-paper5.pdf

https://litux.nl/Books/Books/www.leothreads.com/e-book/oreillybookself/java/exp/ch05_05.htm