In Procedure Division rules, the term identifier means the
  complete specification of a data item. The term refers to
  all words required to make your reference to the item
  unique.  To reference a data item that is a function, a
  function-identifier is used.

  Format 1 -

   data-name [qualification] [subscripting] [reference modification]

  Format 2 -

   data-name [qualification] [indexing] [reference modification]

  Format 3 -

   FUNCTION function-name [ ({argument}...) ] [reference modification]