After reading this, I recall how weird it was to me to think of a process as a person inhabiting a planetary directory tree. I think this metaphor is what kept me from really understanding processes the first time I touched an AIX system coming from my Apple DOS / MS-DOS world. Prior to meeting AIX, there was no persistent directory structure; my first computer didn't even have a tape drive (Commodore PET), so the analogy never even took shape.

I mean, the article talks about the "what", but it makes me wonder about the "why".