; selects the context node if it is an 'elem' element; 
; otherwise selects nothing
;
; Abbreviated XPath: NONE
; Full XPath: self::elem

(define tree 
'(elem
 (@ (name "elem") (id "idz"))
 (para (@) "para")
 (br (@))
 "cdata"
 (para "second par")
 (div (@ (name "aa")) (para (@) "third para")))
 )

; Low-level:
((node-self (ntype?? 'elem))
 tree)

==>
((elem
  (@ (name "elem") (id "idz"))
  (para (@) "para")
  (br (@))
  "cdata"
  (para "second par")
  (div (@ (name "aa")) (para (@) "third para"))))