Warning: italian to english translation was done with the help of Google Translate, therefore it might not be entirely accurate
Have you ever been interested in a certain franchise (be it videogames, anime, manga, visual novel o whatever) you still never tried but, with all the various chapters, sequels, prequels, remakes and timelines comprising it, having no idea where to begin?
Thanks to the Blue Apple diagrams (or BA diagrams), in an eye's blink you can have a clear vision about the exact relationships between the various titles in any series/project, and decide for yourself what's the best path to choose in order to follow it.
The various titles comprising a franchise are arranged as dots in a cartesian chart where the x axis is their release order, while the y axis is their chronological succession according to the series' timeline:
for example, when a title is shown on the upper right to another, it means it is a sequel, while if it's shown on the lower right, it means it's a prequel.
This means, if you want to follow a series exactly in their release order (from the oldest to the newest), all you have to do is to read the chart from left to right; if you want to follow the series according to its own internal timeline (from the one set more in the past to the one more in the future) instead, you have to read the chart from the bottom to the top.
The various titles can be connected by orange lines whose thickness gives informations about how much each one of them requires the others in order to have a clear understanding of the plot; more in detail, the thickness of each one of the 2 ends of a line states how much the title at that end requires seeing the one at the other end to be understood per essere compreso. Some clarifying example:
Blue Apple's diagrams can also represent eventual remasters/remakes and collections: azure lines connect each title to its respective remaster/remake; the line's thickness states in what proportion the former is included into the latter, while the amount of new features added in the latter is represented by the opacity of its dot. Some clarifying example:
When a title includes other previously released chapters precedentemente usciti (either in part, or in their entirety), for example in the case of collections, each one of them is represented by a specific dot stante, all of which are encompassed into a longer one representing the whole title:
And now for some practical examples: