Like Bubblegum Crisis, AD Police was made afterwards but it is a prequel, but neither of those facts suggests which one you should watch first. Well, in that example it doesnt really matter, since they dont have that much to do with eachother, but Bubblegum Crisis is the original, and the recommendation would be to watch that one first, even though AD police is listed as a prequel.
Or like in the Macross Saga, stuff is made in different times, Macross Zero is the newest made sofar, but it is set before any of the other series, but its not recommended to watch it first (even though you can, since all Macross series are pretty much standalones)
I hope I'm not confusing anyone

The viewing order could listed outside of the graph, but it would probably be most useful there then in any other place.