I knew Bert for well over 50 years, and the first word that comes to mind to describe him is "lovable", and the second is "foundational".

It is too early for those of us who loved him to recount "Bert stories" and especially "Bert and Ivan" stories, but Dan has provided the links to the YouTube video CHM tribute to the two brothers. Everyone should also read the Wikipedia article about Bert.

Bert's PhD thesis is most often characterized by its title "Online Graphical Specification Of Procedures", but once you look at it you realize that he was one of the first (if not the first) inventor of "dataflow" programs, and in fact this thesis was central to the many "prior art" definitions to quash lawsuits about dataflow ideas.

Another dimension to Bert's scientific and engineering career that is not mentioned enough is that he was one of the earliest and main drivers of what is called CAD today (a rather small number of people in different places made this happen in the early 60s -- including Bert's brother Ivan -- and Bert focused some of the powerful human and computing resources of Lincoln Labs on this vital technology).

Bert's personality was sunny, friendly, and "sweetly firm", to the point that many people clamored to have him as their manager (including only half-jokingly: Ivan). I was completely thrilled when Parc brought in Bert to run the Systems Science Lab in which my group, Lynn Conway's group, Bill English's group etc were all ensconced.

Bert, as with the other enlightened ARPA research managers knew that "the geese wanted to lay their golden eggs" and the manager's job was to support these efforts, not to try to tell the geese how to lay the special eggs). He was superb at this, and many critical inventions and systems happened because he was the nurturer.

I guess I should tell a "Bert and Ivan" story. Their father was a civil engineer who brought not just blueprints home but gadgets and kits for the two brothers -- who were just two years apart in age -- to play with. Bert would recall that Ivan was so smart that he would just start putting the stuff together while Bert read the manual. At the 95% point Ivan would get stuck and Bert would know what to do next. The two brothers with very different personalities got along wonderfully well over their entire lives, and would occasionally do a company together.

A big deal when the kids were young was their mother driving them down from Scarsdale to Murray Hill to Bell Labs to meet Claude Shannon. Years later at MIT, Shannon wound up being a thesis supervisor of both of their PhDs done a few years apart.

I think most of us from 50+ years ago in the ARPA community just revered and were in awe of the research generations that came before us, especially the one right before us. It was tough to do computing back then, but they didn't let this bother them at all. They would program anything they wanted to have happen -- mostly in machine code -- and they would design and build any hardware they needed to run the programs they needed -- mostly with discrete components and relatively high voltages over sometimes acres of computer.

They showed us how to work and play and design and sculpt and the deep art that lies behind the components. We can never thank them enough, and can only "pay forward" by helping those who come after us.