Norm Hardy is the source of all modern thinking about capabilities. Norm was the chief architect of the KeyKOS operating system, originally Gnosis (Great New Operating System In the Sky). Back during the first golden age of capabilities, in the 1960s and 1970s, Gnosis/KeyKOS was one of a number of capability operating systems. However, by the 1990s only the ideas rooted in KeyKOS continued to grow. All the other branches had fossilized or withered. To a good approximation, everyone today who is excited about capabilities learned it from Norm, or someone who learned it from Norm, etc.
Due to his central role, I invited Norm to give the keynote at OCap 2017
https://www.youtube.com/watch?v=hEDCXTpx0R8&list=PLCq8mSCP664TUdgHl1cD5sDiAmrDoio2pThe KeyKOS operating system is not just an astonishing engineering achievement, it is an astonishing intellectual achievement. As an intellectual achievement, KeyKOS embodies a philosophy of computation that I have spent much of my life trying to understand and explain to the world. I will say more on this elsewhere.
As an engineering achievement, as I say in my introductory remarks to Norm's keynote, KeyKOS is bizarrely close to perfect. For years, my every attempt to find something to improve failed. Jonathan Shapiro had a similar experience but did arrive at genuine improvements with EROS and Coyotos, which provided the crucial bridge to seL4. Today's only practical verified secure OS, seL4, could be verified to solve the whole problem because it built on the KeyKOS design which actually did solve the whole problem.
Several of us have brought some of these insights into other areas of engineering (with apologies to all those I should have included):
* Dean Tribble, Norm, Chip Morningstar, Marc Stiegler, and I brought these insights into modern programming language design (Trusty Scheme, Joule, E, Midori, Dr.SES).
* Bill Frantz, Chip Morningstar, Tyler Close, and I brought these to cryptographic protocols (CapTP, Waterken, SPKI/SDSI). We also built on crucial foundational work by Jed Donnelley that Norm told us about.
* Marc Stiegler, Ka-Ping Yee, Alan Karp, and Mark Lentczner brought capability-based insights to user interface security (CapDesk, Belay), all starting from a user interface koan from Norm: "The clipboard is inherently hostile to user interface security. Drag-n-drop is inherently friendly to it."