bapi

Hi experts ,

I have seen all bapi function modules defined using separate bapi structure . i mean in import , export parameters like example BAPIMEPOHEADER , where all po header data is available.

is there any reason why there is aways change in fields like in PO_NUMBER instead of EBELN in the bapi structure.

Why bapi uses separate own structure and field names .

Pls.help about this .

Regards,

kiran.