Four rules for archaeologist: how to dig out an IT system

There is an information system. It works, users are satisfied, the customer is satisfied. The team is at least not disgusted. 

And then: someone quit, you need to unload the team a little, or the customer asked for the development of the system.  

Then you - an analyst - appear as a new employee - in exchange for another, or a new member - now you are part of a team. 

What is known about the system? Are the schemes and processes described? Is it described how the system works and what each part does? Is it reflected what surrounds the system, and how is the environment connected to the system? 

If practically nothing is of this and you have nothing to rely on - you should be here. 

If you do not know how to get it all, I will share our experience. If you know,  I will listen to your comments with pleasure. 

As a result, you will learn the 4 rules of the archaeologist of information systems and how to apply them at the excavations.