Induction is bottom-up.
Recursion is top-down.
In parsing, YACC is bottom-up, PEG is top-down.
YACC is LR(k), PEG is recursive-descent.
YACC is context-free, PEG can depend on context.
LR(k) is theoretical, PEG is practical.
Semi-colons exist in PLs because of YACC. PEG doesn't require semi-colons in PLs.
Possible rewording: top-down is operational, whereas bottom-up is declarative.
Top-down implies the use of a Stack. Bottom-up does not.
[Use of a Stack defies parallelism.]
 PEG means Parsing Expression Grammar, see https://bford.info/packrat/. PEG is like REGEXPs on steroids.
 PL means Programming Language.
 Question to self: Is this a correct characterization?
 A stack of breadcrumbs - to "remember" where you were.
 Time is also known as History. History is also known as State.
 Lack of f(t) has been decried by Ilya Prigogene (Nobel laureate, "Order Out of Chaos") and Grace Hopper.