The C in CAP and the C in ACID are not the same C. Consistency in the ACID sense means that all constraints are met, Consistency in the CAP sense means all servers have the same data.
fwiw, here is the formal version of the theorem from the gilbert/lynch proof paper:
Theorem 1. It is impossible in the asynchronous network model to implement a read/write data object that guarantees the following properties: * Availability, * Atomic consistency, in all fair executions (including those in which messages are lost).
Comments
The C in CAP and the C in ACID are not the same C. Consistency in the ACID sense means that all constraints are met, Consistency in the CAP sense means all servers have the same data.
I know. I actually explained this not too long ago here: http://news.ycombinator.com/item?id=1191003
But what I'm saying here is: You cannot have ACID transactions without the C in CAP.
fwiw, here is the formal version of the theorem from the gilbert/lynch proof paper:
Theorem 1. It is impossible in the asynchronous network model to implement a read/write data object that guarantees the following properties: * Availability, * Atomic consistency, in all fair executions (including those in which messages are lost).