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BNF/EBNF variants

Style	Name and link	Rule	Items		Concat (default space)	Choice	Optional	Repetition					Grouping	Other	Comment
Style	Name and link	Rule	Terminal	Non Terminal	Concat (default space)	Choice	Optional	0 or more	1 or more	n	n to m	Other	Grouping	Other	Comment
BNF	BNF (Algol 60)	<name>::=...	...	<...>		\|	note1	note2	note3						note5
Intermediate	ANSI C	name: ...	bold	italics		indented line one of	..._opt	note2	note3						note5
Intermediate	BNF-like description of URLs	name ...	...	...		\|	[...]	note2	note3						note5
Wirth	Wirth	name=... .	"..."	...		\|	[...]	{...}	note4				(...)
	SAIF and Bungisoft	<name>::=...	"..."	<...>		\|	[...]	{...}	note4				(...)		note5
	EBNF from Compiler Basics by J.A.Farrell	name:==...	'...'	...		\| or [...,...]	[...]	{...}*	{...}						note5
	Pascal EBNF Definition	name ...	"..." bold	<...>		\|	[...]	{...}	note4				(...)		note5
	ISO Extended Pascal	name=... . name>... .	`...'	...		\|	[...]	{...}	note4				(...)		(...)
	ISO EBNF	name=...;	'...' "..."	...	,	\|	[...]	{...}	{...}-	n*...			(...)	...-... ?...?	(...)
ABNF	EBNF from RFC822 (superceded by ABNF)	name=...	integer "..."	... <...>		/	[...] *1...	*...	1*...	n*n...	n*m...	n#m...	(...)		;...
ABNF	ABNF (RFC2234)	name=...	integer "..."	... <...>		/	[...] *1...	*...	1*...	n*n...	n*m...		(...)		;...
XBNF	XBNF	name::=... .	"..."	...		\|	O(...)	#(...)	N(...)			L(...,...)	(...)	...&... ...~...	any text not in a rule
Regular expression	ISO Minimal BASIC	name=...	ITALICS	italics		/	...?	...*	note4						note5
Regular expression	EBNF for XML	name::=...	"..." '...'	...		\|	...?	...*	...+				(...)	...-... [wfc:...] [vc:...]	/.../

... indicates some other part of the grammar e.g. a terminal literal, or a non-terminal name, or even a series of such items.

Notes:

BNF can express an optional part by e.g.:
```
optionalb ::= a b c d | a c d
```
BNF can express 0 or more repetitions by e.g.:
```
list ::=  | listitem list
```
BNF can express 1 or more repetitions by e.g.:
```
list ::= listitem | listitem list
```
Notations that provide 0 or more repetitions but not 1 or more repetitions can simulate the latter. e.g. Wirth's EBNF can express 1 or more repetitions by e.g.:
```
list : listitem { listitem }
```
A grammar rule that is only instanced once is often actually being used as a comment

Here are some more versions of EBNF to be added to the table above.

Parser generators, such as those listed here or here, and various others, such as PRECC and SDF
Possibly abstract grammars, such as ASN.1 or Zephyr ASDL

WBNF (D.S.Wile): Popart or here? or (pdf) or (pdf)

(badly converted from pdf, needs checking!)
concatenation:		block := declarations statements; 
alternation:		declaration := function | procedure; 
constant lexical items:	plusop := '+' | '-';
optionality:		int := 'integer' identifier { 'in' range }; 
"Kleene plus":		statements := statement + ; 
lists with separators:	funcall := identifier '(' expr ^ ', ')'; 
precedence:		expr := < ('+' | '-'), ('*' | '/'), '^' > primitive; 
nesting:		'declare' ('integer' | 'real') variable; 
variable lexical items:	LEXEME <| alphanumeric;

TXL
How far can EBNF stretch?
OASIS maintains DocBook, which includes an XML standard for EBNF but it doesn't go into enough detail for our purposes. The DocBook EBNF Document Type

UP to more information about BNF, Syntax Diagrams and EBNF

This page is maintained by and copyright © Pete Jinks [last modified 12/Mar/2004] suggestions, corrections etc. welcome You are welcome to make educational, not-for-profit use (else what would be the point!) but please give due credit.