Hi Kimbo,

Not disagreeing with you, but the point I was trying to get across is who you would need to ask to get an understanding of what the As-IS was. I would also say that if you are going to go via external 3rd party vendors, they wont care too much about your internal processes. All they will be interested in is the interfaces, which any external system will need to make sure it can integrate with. 

Whilst you are having those discussions (which take quite a while) then you can go through the internal processes, but in order to know who to ask, you first need to find out who the key stakeholders are. Those that I mentioned, The Developer and The Product Owner should have had a good idea who internally they spoke to when they first built the system, therefore you save some time by speaking to the relevant experts. Remember, the experts aren't always those in power.