Payables using XML

I would like to import in a Payables Transaction into Dynamics GP.  The source will be an xml generated by another system.  Is there any assistance or guides on how to set this up?  The owners of the other system want the xml schema or format as well - how would I get that?  Finally the transaction may have multiple distribution lines.  I usually use a row count to tell scribe when to insert the transaction.  Will that work with an xml?