anchor.diff:   	)*
    ;
   
  + /** Upper or lower case letter */
    LETTER
    :
    	(
  
positive.code:  	| '<='
   ;
  
   bool_val
   :
   	'TRUE'
   	| 'FALSE'
   ;
  
   categ_attr
   :
   	ID '.' ID
   ;
  
   str_val
   :
   	categ_attr
   	| STRING
   ;
  
   str_comp
   :
   	'='
   	| '<>'
   ;
  
   ID
   :
   	LETTER
  
negative.code:  	| bool_val
   ;
  
   /** Possible actions to be defined */
   action_id
   :
   	'PERMIT'
   	| 'DENY'
   ;
  
   /** Boolean operations */
   bool_op
   :
   	'&'
   	| '|'
   ;
  
   /** Boolean comparators */
   bool_comp
   :
   	'='
   	| '!='
   ;
  
   /** Arithmetic values */
   arit_val
   :
   	NUM
   	| categ_attr
   ;
  
   /** Arithmetic comparators */
   arit_comp
   :
   	'='
  