Has "top" ($\top$) been removed from or relegated to a much more minor role in denotational semantics? If so, when and why?
I see older papers and books talking about both "top" and "bottom" ("bot", $\bot$), but it seems like newer work only refers to bot. I vaguely recall seeing a reference somewhere that said that top wasn't used anymore or wasn't necessary, but I don't know where that was and I don't know anything about the transition away.
I'm reading a paper from 1979 about applying denotational semantics to databases and null values ("Null Values in Data Base Management: a Denotational Semantics Approach" by Yannis Vassiliou) that makes heavy use of both bot and top, and I'd like to understand what a more modern take on that might be. Any relevant references on that angle would also be greatly appreciated.