EDI: Syntax error in IDoc (segment cannot be identified)

hi,

i m working with ORDERS01. i have syntax error 26 as put in subject line. Reason is

" The segment E1EDP02 does not occur at the current level of the basic type ORDERS01 (extension )"

in IDoc E1EDP02 does not appear as child to E1EDP01.

what is the reason for it ?

can u also tell me in which routine/function module the syntax is checked, so i can have a breakpoint and debug it.