Grammar Specs

The following Grammar Specs are used for writing rules for the UNDL Foundation tools (IAN, EUGENE, SEAN, NORMA, etc.).

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 Indexation)
#	index for sub-NLWs	#01 (see #Indexation)
=	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

Node

A node is the most elementary unit in the graph. It is the result of the tokenization process, and corresponds to the notion of "lexical item". At the surface level, a natural language sentence is considered a list of nodes, and a UNL graph a set of relations between nodes.

Relation

In order to form a natural language sentence or a UNL graph, nodes are inter-related by relations. In the UNL framework, there can be three different types of relations: linear, syntactic or semantic.

Hyper-Node

A hyper-node is a sub-graph, i.e., a node containing relations between nodes.

Hyper-Relation

A hyper-relation is a relation between relations.