NOT Python: Taxonomy list reference

[ej]

    I hope you will forgive this being a bit off subject, but this is about
the smartest list of people I know.  I came across a list in the past while
studying OO methdology stuff. The list was trying to make the point of the
problem classification systems often run into (i.e., often things belong in
more than one group simultaneously).

The list reads something like this:

1. Beasts that belong to the king
2. Great beasts
3. Furry beasts
4. Unicorns and other magical beasts.
5. Beasts with four hooves.
...

    I can't remember if I was reading a web article, or one of my O'Reilly
books (I have many, many of these - not much hope of finding it by just
browsing through them), or one of my other books, or what... (I checked
Booch's "OO Analysis and Design" - didn't see it.) As great as Google is, I
have tried many different searches but am still coming up empty-handed.
Wikipedia is also pretty great, but again I can't seem to find it.

Any Pythonistas out there know the list I am referring to and could point me
to it?  Thanks for your time! :)