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DBKit was basically discarded and redesigned as EOF, which did make it into the Mac. I'm not sure EOF made it into the iPhone, but the tech lead on EOF Richard Williamson, became tech lead for the first iPhone application stack.
His strategy was demanding an unreasonable level of excellence and being indifferent to how the people who worked for him might be impacted. Those that survived got to work at a company where everyone was extremely talented. People who couldn't stand the heat were free to work elsewhere. It's arrogant, but it did allow him to create a uniquely creative and effective environment.
And keep in mind that if the Apple acquisition of NeXT hadn't worked out -- an acquisition that Steve was opposed to, I believe -- NeXT could have ended up in the dustbin of history, and there would be no OSX, iMac, iOS, iPod, or iPhone. So in many ways, the approach could have backfired, but in this case, it didn't.
That said, Steve's intuition was right. We pushed on the impossible for a while and found a way to make the actual technology work the way he liked, by using an entity-relationship model to object-pointer mapping. And that approach later became the standard paradigm for database application building tools across the industry.
Steve made unreasonable demands, but he was on the right side of history sufficiently often that top people wanted to be on his team and tolerated the craziness of it.
DBKit was later rewritten with a real architecture which became Enterprise Objects Framework (EOF).
The general principle in the brain is that the individual neurons (there are 25 billion in the cerebral cortex) represent statistically frequent occurrences of experienced phenomena. So if you know a lot about dogs and interact with dogs a lot, you will have a lot of neurons that "represent" different things about dogs (dog categories, dog behaviors, aspects of dog appearances, etc.).
The neurons "represent" perceptual experiences in a collective way called a population code. In one study on humans, a neuron was found that fired when viewing pictures of Jennifer Aniston but only when Brad Pitt was not in the photo. This does not mean the neuron had the sole job of representing Jennifer Aniston, but only that it was "tuned" to this perceptual occurrence. The tunings of neurons are distributed to "cover" in a statistical fashion the range and components of experiences. This particular human subject had perhaps watched many episodes of Friends.
What is still unknown is how the structure of a visual scene is represented. Neurons have been found for edges, contours, shapes, motion, depth, and objects. The mystery is how they all work together to parse and compose the scene. This is hard to determine because it is usually only possible to "listen" in on a few neurons at a time with electrodes, whereas it takes hundreds of millions to represent the visual world.
Regarding how visual mental imagery works, here is a post I made on Quora about that in case it is of interest: https://www.quora.com/How-can-we-see-images-in-our-minds