UNL sentence

UNL sentences, or UNL expressions, are sentences of UNL. They are hypergraphs made out of nodes (Universal Words) interlinked by binary semantic Universal Relations and modified by Universal Attributes. UNL sentences have been the basic unit of representation inside the UNL framework.

Syntax

According to the UNL Specs, there are two different ways of representing UNL sentences: the table format and the list format. In the list format, UWs and relations are represented separately; in the table format, they constitute a single structure.

List Format

The syntax for UNL sentences in the list format is the following:

<UNL sentence>	::=	"[W]" <list of UWs> "[/W]" [ "[R]" <list of relations> "[/R]" ]
<list of UWs>	::=	<UW+attributes> [<UW+attributes>...]
<UW+attributes>	::=	<UW>{“:”<Scope-ID>}}[<attribute list>]”:”<UW-ID>
<list of relations>	::=	<binary relation>[<binary relation>...]
<binary relation>	::=	<source node><relation[":"<Scope-ID>]<target node>
<source node>	::=	<UW-ID>
<target node>	::=	<UW-ID>

Table Format

The syntax for UNL sentences in the table format is the following:

<UNL sentence>	::=	<list of relations>
<list of relations>	::=	<binary relation>[<binary relation>...]
<binary relation>	::=	<relation> [“:”<Scope-ID>] “(“ <source node> , <target node> ")"
<source node>	::=	<UW+attributes>
<target node>	::=	<UW+attributes>
<UW+attributes>	::=	<UW>{“:”<Scope-ID>}}[<attribute list>]”:”<UW-ID>

Where
" and " indicate a predefined delimiter
< and > indicate a non-terminal symbol
{ and } indicate a range
[ and ] indicate an omissible part
... indicates more than 0 times repetition of the front part
::= indicates the left part can be replaced by the right part