

1.

input tokens A, B, C, D ...


2.


a: b c d e

item sequence b, c, d, e can be replaced with item a




3.

sequences may contain input tokens (terminal symbols) or items (non-terminal symbols)


a: b A c D E



4.

loops may occur within the rule itself or across multiple rules


a: a B
 : B


	B  B  B
	|  |  |
	a  |  |
	 \/   |
	  a  /
	   \a
	    

a: c D E
 : F


c: a D G
 : K





