I hope you now have a clear idea of the basic structure of the model I am proposing: The stack of borrows, the freeze flag, and references tagged with the time at which they got created.
The full model is not quite as simple, but it is not much more complicated either.
-We need two add just two more concepts: Retagging and barriers.
+We need to add just two more concepts: Retagging and barriers.
### 4.1 Retagging