Don't want to show off, but it seemed quite readable to me, once you notice that the arrows have numbers..

It shows many interesting details (the only API command seems to be Patch. There are two sync phases on the client, one to determine what to send to the server, one to determine what to merge upon server response). I quite like diagrams :))

What do the numbers represent?

Lifecycle of data as it changes, apparently.

The diagram is horrible and doesn't really explain anything. I want to know what it is, not stare at some cryptic diagram for ten minutes.