I am reading the paper Making geo-replication fast as possible, consistent when necessary by Li et al. in which they propose a geo-replication system called "RedBlue Consistency". They have a table which compares a couple of systems that have implemented geo-replication with several desired properties. One of the properties is called "stable histories", and their description is:
the system should provide a set of stable histories, meaning that user actions cannot be undone;
I don't fully understand this part, what do they mean by "user actions cannot be undone"?
Here is a link to the paper and a video of the talk: https://www.usenix.org/conference/osdi12/technical-sessions/presentation/li