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|  |   |  | #REDIRECT [[Grammar]] | 
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|  | == Basic symbols ==
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|  | {| border="1" cellpadding="2" align=center
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|  | |+Basic symbols used in UNL grammar rules
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|  | !Symbol
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|  | !Definition
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|  | !Example
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|  | |-
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|  | |align=center|<nowiki>^</nowiki>
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|  | |not
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|  | |^a = not a
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|  | |-
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|  | |align=center|{ | }
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|  | |or
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|  | |<nowiki>{a|b}</nowiki> = a or b
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|  | |-
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|  | |align=center|%
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|  | |index for nodes, attributes and values
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|  | |%x (see [[#Indexes|below]])
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|  | |-
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|  | |align=center|#
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|  | |index for sub-NLWs
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|  | |#01 (see [[#Indexes|below]])
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|  | |-
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|  | |align=center|=
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|  | |attribute-value assignment
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|  | |POS=NOU
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|  | |-
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|  | |align=center|!
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|  | |rule trigger
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|  | |!PLR
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|  | |-
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|  | |align=center|&
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|  | |merge operator
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|  | |%x&%y
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|  | |-
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|  | |align=center|?
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|  | |dictionary lookup operator
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|  | |?[a]
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|  | |-
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|  | |align=center|“ “
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|  | |string
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|  | |"went"
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|  | |-
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|  | |align=center|[ ]
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|  | |natural language entry (headword)
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|  | |[go]
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|  | |-
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|  | |align=center|[[ ]]
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|  | |UW
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|  | |[[to go(icl>to move)]]
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|  | |-
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|  | |align=center|( )
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|  | |node
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|  | |(a)
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|  | |-
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|  | |align=center|//
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|  | |regular expression
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|  | |/a{2,3}/ = aa,aaa
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|  | |}
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|  | == Basic Concepts ==
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|  | ;The differences between "", [] and [[]]
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|  | :Double quotes are always used to represent strings: "a" will match only the string "a"
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|  | :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])
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|  | :Double square brackets are always used to represent UWs: <nowiki>[[a]]</nowiki> will match the node associated to the UW <nowiki>[[a]]</nowiki>
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|  | ;Predefined values (assigned by default)
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|  | :SCOPE - Scope
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|  | :SHEAD - Sentence head (the beginning of a sentence)
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|  | :STAIL - Sentence tail (the end of a sentence)
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|  | :CHEAD - Scope head (the beginning of a scope)
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|  | :CTAIL - Scope tail (the end of a scope)
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|  | :TEMP - Temporary entry (entry not found in the dictionary)
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|  | :DIGIT - Any sequence of digits (i.e.: 0,1,2,3,4,5,6,7,8,9)
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