A company I used to work for built online shopping carts. We were building one for an industrial company who's inventory system ran on an AS/400, and we were doing an integration. I had ZERO familiarity with IBM mainframes at the time and presumed (wrongly) that it ran some flavor of UNIX. I was to work with their lead developer to get the integration going. He was maybe late 50s, I never met him face to face, only over the phone. I suggest that they build a "simple JSON or XML API" for us to connect to. This makes their lead very uncomfortable. He does NOT want to put the machine on the public facing Internet (reasonable enough) and has never worked with XML or JSON. He instead wants to set up a system where hourly it would email us CSV diffs. Maintaining data working from diffs sounded like a nightmare to me, plus I'd never programmaticly worked with receiving emails. Whole thing sounded iffy. Plus understanding their data model it would not be shoved into CSV without a fight. After a bunch of back and forth (weeks) we work out a system where the server would upload a combination of CSV and XML to an FTP share we controlled and I could reprocess the data hourly. It actually worked reasonably well. I'm curious if it's still in operation, I've long forgotten the name of the company we built this for, there were just so many.