[O] About `open formula'

[Xue Fuqiao]

In (info "(org) Editing and debugging formulas"):

    `<TAB>     (`org-table-fedit-lisp-indent')'
          Pretty-print or indent Lisp formula at point.  When in a line
          containing a Lisp formula, format the formula according to
          Emacs Lisp rules.  Another <TAB> collapses the formula back
          again.  In the open formula, <TAB> re-indents just like in
          Emacs Lisp mode.  

What does the `open formula' mean?  I've searched the Org manual/FAQ and web, 
and I only found this:
http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part2.html

But it seems that the `open formula' doesn't mean this.
-- 
Best regards, Xue Fuqiao.
http://www.emacswiki.org/emacs/XueFuqiao