anchor.diff:      ;
   
   atomicTypeSpecifier
  -    : IDENTIFIER // TODO: specify atomic type names as part of the grammar?
  +    : IDENTIFIER
       ;
   
   listTypeSpecifier
  
positive.code:     ;
  
  sortByItem
      : qualifiedIdentifier sortDirection?
      ;
  
  qualifiedIdentifier
  
negative.code:     ;
  
  unit // NOTE: Using plurals here because that's the most common case, we could add singulars, but that would allow "within 5 day"
      : dateTimePrecision
      | pluralDateTimePrecision
      | 'week'
      | 'weeks'
      | 'u'STRING // UCUM syntax for units of measure
      ;
  
  