Question

I guess the same logic is applied in both of them, i.e replacing the matched strings with the corresponding non-terminal elements as provided in the production rules.

Why do they categorize LL as top down and LR as bottom-up?

Answer 1

Bottom up parsing:

Bottom-up parsing (also known as
shift-reduce parsing) is a strategy
for analyzing unknown data
relationships that attempts to
identify the most fundamental units
first, and then to infer higher-order
structures from them. It attempts to
build trees upward toward the start
symbol.

Top-down parsing:

Top-down parsing is a strategy of
analyzing unknown data relationships
by hypothesizing general parse tree
structures and then considering
whether the known fundamental
structures are compatible with the
hypothesis.