<s>
Syntax	B-Application
diagrams	I-Application
(	O
or	O
railroad	B-Application
diagrams	I-Application
)	O
are	O
a	O
way	O
to	O
represent	O
a	O
context-free	O
grammar	O
.	O
</s>
<s>
Early	O
books	O
using	O
syntax	B-Application
diagrams	I-Application
include	O
the	O
"	O
Pascal	O
User	O
Manual	O
"	O
written	O
by	O
Niklaus	O
Wirth	O
(	O
diagrams	O
start	O
at	O
page	O
47	O
)	O
and	O
the	O
Burroughs	O
CANDE	B-Operating_System
Manual	O
.	O
</s>
<s>
Railroad	B-Application
diagrams	I-Application
are	O
visual	O
,	O
and	O
may	O
be	O
more	O
readily	O
understood	O
by	O
laypeople	O
,	O
sometimes	O
incorporated	O
into	O
graphic	O
design	O
.	O
</s>
<s>
The	O
canonical	O
source	O
defining	O
the	O
JSON	B-General_Concept
data	B-General_Concept
interchange	I-General_Concept
format	O
provides	O
yet	O
another	O
example	O
of	O
a	O
popular	O
modern	O
usage	O
of	O
these	O
diagrams	O
.	O
</s>
<s>
The	O
representation	O
of	O
a	O
grammar	O
is	O
a	O
set	O
of	O
syntax	B-Application
diagrams	I-Application
.	O
</s>
<s>
One	O
possible	O
syntax	B-Application
diagram	I-Application
for	O
the	O
example	O
grammars	O
is	O
below	O
.	O
</s>
<s>
Note	O
that	O
while	O
the	O
syntax	O
for	O
the	O
text-based	O
grammars	O
differs	O
,	O
the	O
syntax	B-Application
diagram	I-Application
for	O
all	O
of	O
them	O
can	O
be	O
the	O
same	O
because	O
it	O
is	O
a	O
metalanguage	O
.	O
</s>
