Grammar Specs

Basic symbols

Basic symbols used in UNL grammar rules

Symbol	Definition	Example
^	not	^a = not a
{ | }	or	{a|b} = a or b
%	index for nodes, attributes and values	%x (see below)
#	index for sub-NLWs	#01 (see below)
=	attribute-value assignment	POS=NOU
!	rule trigger	!PLR
&	merge operator	%x&%y
?	dictionary lookup operator	?[a]
“ “	string	"went"
[ ]	natural language entry (headword)	[go]
[[ ]]	UW	[[to go(icl>to move)]]
( )	node	(a)
//	regular expression	/a{2,3}/ = aa,aaa

Basic Concepts

The differences between "", [] and [[]]

Double quotes are always used to represent strings: "a" will match only the string "a"

Simple square brackets are always used to represent natural language entries (headwords) in the dictionary: [a] will match the node associated to the entry [a] retrieved from the dictionary, no matter its current realization, which may be affected by other rules (the original [a] may have been replaced, for instance, by "b", but will still be indexed to the entry [a])

Double square brackets are always used to represent UWs: [[a]] will match the node associated to the UW [[a]]

Predefined values (assigned by default)

SCOPE - Scope

SHEAD - Sentence head (the beginning of a sentence)

STAIL - Sentence tail (the end of a sentence)

CHEAD - Scope head (the beginning of a scope)

CTAIL - Scope tail (the end of a scope)

TEMP - Temporary entry (entry not found in the dictionary)

DIGIT - Any sequence of digits (i.e.: 0,1,2,3,4,5,6,7,8,9)