grammar N3Grammer
	rule document
		statements
	end
	
	rule statements
		(space / (statement / directive) space* ('.' space*)? )*
	end
	
	rule statement
		subject space+ property_list
	end
	
	rule subject
		node
	end
	
	rule verb
		">-" prop "->"      # has xxx of 
		/ "<-" prop "<-"    # is xxx of 
		# / # / operator     # has operator:xxx of??? NOT IMPLMENTED
		/ prop              # has xxx of -- shorthand
		# / "has" prop        # has xxx of
		# / "is" prop "of"    # is xxx of
		/ "a"               # has rdf:type of
		# / "="               # has daml:equivaent of
	end
	
	rule prop
		node
	end
	
	rule node
		uri_ref / anonnode / 'this'
	end
	
	rule anonnode
		"[" space* property_list space* "]"  # something which ...
		/ "{" statementlist "}"  # the statementlist itself as a resource
		/ "(" nodelist ")" {
			def anonnode; true; end
		}
	end
	
	rule property_list
		verb space+ object_list space* ";" space+ property_list
		/ verb space+ object_list
		/ ":-" anonnode  #to allow two anonymous forms to be given eg [ a :Truth; :- { :sky :color :blue } ] )
		/ ":-" anonnode ";" property_list
		/ '.'
	end

	rule object_list
		object "," space* object_list / object
	end

	rule directive
		'@prefix' space+ nprefix:nprefix? ':' space+ uri_ref:uri_ref {
			def directive; true; end
		}
	end
	
	rule uri_ref
		qname / "<" uri:URI_Reference ">"
	end
	
	rule qname
		nprefix ":" localname / ':' localname
	end
	
	rule object
		subject / literal
	end
	
	rule literal
  	(string_single / string_multi) ("^^<" uri:URI_Reference ">" / "@" language )?
	end
	
	rule language
		[a-z]+ ( "-" [a-z0-9]+ )*
	end

	rule localname
		fragid
	end
	
	rule URI_Reference
		[^{}<>]*
	end
	
	rule nprefix
		((alpha / "_") alphanumeric*)
	end

	rule fragid
		alpha alphanumeric*
	end

	rule alpha
		[a-zA-Z]
	end
	
	rule alphanumeric
		alpha / [0-9] / "_"
	end
	
	rule space
		[ \t\n\r]+ / comment
	end
	
	rule comment
	  '#' (![\n\r] .)*
	end

  # " constant-value-with-escaping "
	rule string_single
		'""' !["] / '"' string_single_char+ '"'
	end

	rule string_single_char
    !["\n\r] (
      ("\\"
        [\\\"nrt]
      / ( "u" hexdigit hexdigit hexdigit hexdigit )
      / ( "U" "00" hexdigit hexdigit hexdigit hexdigit hexdigit hexdigit)
      )
    / .)
	end

  rule hexdigit
    [0-9a-fA-F]
  end
  
  # """ constant value with escaping including single or double occurrences of quotes and/or newlines """	
	rule string_multi
		'"""' string_multi_char* '"""'
	end

	rule string_multi_char
		!'"""' . # something like this; need to think about it some more	
	end
		
end