| Type of Grammar | Constraints | Automata |
| Phrase Structure | A -> B |
Turing Machine (Unrestricted) |
| Context Sensitive | aAb -> aBb |
Linear Bounded Automata (N-grams, Unification) |
| Context Free |
A -> B Constraint: A is a non-terminal. Equivalent to: A -> w A -> BC where "w" is a terminal; B,C are non-terminals (Chomsky normal form) |
Push down automata (JSGF, RTN, Chart Parsing) |
| Regular |
A -> w A -> wB (Subset of CFG) |
Finite-state automata (Network decoding) |