Regular Grammar

Let be a CFG. G is called a regular grammmar if every production takes one of the three forms

where .

.

G:

a-a-a has two trees
G is AMBIGUOUS.

Def. A CFG G is ambiguous if there is at least one string in L(G) having two or more drivation trees.

Def. A CFL is inherently ambiguous for which every CFG is ambiguous.

e.g.

is inherently ambiguous.

has two trees.