Implementing GTM without OTM

Hello community

I must implement GTM alone, the client is not interested in having OTM.

So here is the problem: I need to create a shipment from an 3er party xml integration file. This integration must have all the necessary elements (items, orders, locations, shipment, etc) to allow the automatic creation (through agents) of the shipment and its corresponding Trade Transaction.

Do any of you have information on how this integration file should be composed? Any reading material to guide me?

I found that this type of integration is called SAW - Shipment As Work, but not many more so far.