What is the mathematical machine on which both top-down and bottom up parsers are based?

What is the mathematical machine on which both top-down and bottom up parsers are based?

. Describe three advantages of LR parsers.

. What was Knuths insight in developing the LR parsing technique?

. Describe the purpose of the ACTION table of an LR parser.

. Describe the purpose of the GOTO table of an LR parser.

. Is left recursion a problem for LR parsers?