EDI through VAN

Hi All,

I am trying to pull EDI 850 from VAN.
For this I can use the VAN service to get the EDI data and post it to TN.

My query is that if the 850 I receive from the VAN is of different structure then of the one buit in 850 then do I have to create the schema for the same and register in TN.

Secondly,do I need to create TPAs’?

Once I create the document type and processing rules and submit the document to the develope what steps I should follow to convert it to a PO flat file.