From the article:
>Any Oberon procedure can be made available to the user as system command, provided certain conventions are followed. They are known as Tools. [..]
>It is possible to allow such Tools to act on user interface elements selected by the user.
This is a way more flexible UX/UI paradigm than any OS out there provides.
Symbolics Genera also adopted this approach. Here are some good posts about it on alt.os.multics from Dan Weinreb:
https://groups.google.com/forum/#!search/multics$20commands$...
You can read the Project Oberon 1992's book, sections 3.3 and 3.4 as starting point.
http://www.ethoberon.ethz.ch/WirthPubl/ProjectOberon.pdf
Then you can follow up with the 2003's edition.
https://www.inf.ethz.ch/personal/wirth/ProjectOberon/index.h...
With a stop in the last pure Oberon iteration, Oberon System 3 Gadgets.
http://www.ethoberon.ethz.ch/ethoberon/tutorial/
Oberon Companion describes gadgets and tools
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.472...
The existing PDF book has a couple of rendering issues, but if you install BlueBottle, it has Oberon System 3 as demo application, with the original book in Oberon rich text format (not to mix with RTF).
https://www.youtube.com/watch?v=t6NMJh0noDk&index=35&list=WL...
Which by the way, also describes the Tools on its manual, A2 User Guide and Application Description
http://www.ocp.inf.ethz.ch/wiki/Documentation/Front
https://github.com/btreut/a2
The surviving ISO images
https://sourceforge.net/projects/a2oberon/files/
From the article:
>Any Oberon procedure can be made available to the user as system command, provided certain conventions are followed. They are known as Tools. [..]
>It is possible to allow such Tools to act on user interface elements selected by the user.
This is a way more flexible UX/UI paradigm than any OS out there provides.