From Operating System Concepts.
The terminology just caught my ear -- relativistic theories in computer science. A problem in computer science is atomic execution -- running a set of steps in the right order and either finishing all the steps or reverting to the state before having done any. For example, you want Facebook posts to be axiomatic -- either your post goes through completely or it fails -- you don't want the text to work without the image or the image with garbled text, etc..
It's a hard problem on one computer where interrupts can suddenly cause the processor to do something else, or multiple cores might have other code messing with the variables you need to access exclusively. The diagram is talking about computing distributed over multiple computers where the problem becomes, I think, very hard.