Well, that graph was completed after 4 lectures iirc. Not a huge commitment for anybody who's willing to learn by themselves. I thought OP's doubt were regarding very basic things and all of those can be accommodated in that graph. 1) I know that graph isn't the most comprehensive. It doesn't capture all the details but it's a good start for beginners. If OP's having doubts like that, I suspect they're new to this. 2) Sure they could come up with different graphs, but they wouldn't be wrong, would they? We'll have to agree to disagree here, I know that's a very high level graph, but imo, it's not useless. Of course if there's something better, go for it. This is, by no means, the best illustration there is.