Take a look at the "Slot" package in Pharo.
There's "Examples" and "Examples-Associations" (first class relations) tags.

Peter

On Sat, Oct 7, 2017 at 1:32 PM, Ben Coman <btc@openinworld.com> wrote:
Just wondering what was the status of Slots regarding "first class relations" described in "Flexible Object Layouts" - and availability of examples/tutorials.
https://core.ac.uk/download/pdf/51216612.pdf

cheers -ben