anchor.diff:      ;
   
   sortByItem
  -    : qualifiedIdentifier sortDirection?
  +    : expressionTerm sortDirection?
       ;
   
   qualifiedIdentifier
  
positive.code:     ;
  
  unit // NOTE: Using plurals here because that's the most common case, we could add singulars, but that would allow "within 5 day"
      : 'years'
      | 'months'
      | 'weeks'
      | 'days'
      | 'hours'
      | 'minutes'
      | 'seconds'
      | 'milliseconds'
      | 'u'STRING // UCUM syntax for units of measure
      ;
  
  
negative.code:     ;
  
  atomicTypeSpecifier
      : IDENTIFIER
      ;
  
  listTypeSpecifier
  