If
u
0
Þ
n
u
n
[
p
] for some
n
³
1, then
u
0
properly
derives
u
n
in
G
, written as
u
0
Þ
+
u
n
[
p
].
If
u
0
Þ
n
u
n
[
p
] for some
n
³
0, then
u
0
derives
u
n
in
G
, written as
u
0
Þ
*
u
n
[
p
].
Example:
Consider
a
A
b
Þ
a
aBb
b
[
1
:
A
®
aBb
], and
aa
B
bb
Þ
aa
c
bb
[
2
:
B
®
c
].
Then,
a
A
b
Þ
2
aa
c
bb
[
1 2
],
a
A
b
Þ
+
aa
c
bb
[
1 2
],
a
A
b
Þ
*
aa
c
bb
[
1 2
]
Sequence of Derivation Steps 2/2
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