Thierry,
It does take a bit to wrap your head around. Here's a couple previous threads on it where I've given some detailed examples that I think should be useful in understanding the relationships on dependencies and secondary slot types.
https://www.rdmprotocol.org/forums/s...highlight=slot
https://www.rdmprotocol.org/forums/s...highlight=slot
We also did a Webinar on this topic. You'll find about halfway through it we go through some concrete examples and detailed explanations on Slot_Info.
https://www.youtube.com/watch?v=-5BmsJ7CeFE