ㅁ sequence of replacements of structure names by layouts on RHS, starting from the start nonterminal
Replacement by grammar and transition order determines derivation type
Is called a derivation in G of
math: w_n \, from \,\, w_0 with derivation length n - so w is Sentential Form- Since CFG has ambiguity(make logical error) in derivation order (so we can pre-detect by syntax error)
Left-most derivation
Always replace(terminalize) left-most variable
Right-most derivation
Always replace right-most variable
- make different Parse tree
Top-down approach 1. left-recursive grammar - can occur infinite recursive → so make prime and divide to right-recursive 2. right-recursive grammar