Good point, and well-taken. As I mention in http://www.bailis.org/blog/hat-not-cap-introducing-highly-av... (and devote an full section to in the paper, including documented isolation anomalies like lost updates, write skew, and anti-dependency cycles), there are many guarantees that aren't achievable in a highly available environment. Our goal is to push the limits of what is achievable, and, by matching the weak isolation provided by many databases, hopefully provide a familiar programming interface.

As I tried to stress in the post, we aren't claiming to "beat CAP" or provide "100% ACID compliance"; we're attempting to strengthen the semantic limits of highly available systems. I intended "HAT, not CAP" as a play on acronyms, not as a claim to achieve the impossible.

edit: We're also certainly not claiming to have a "CA" solution, whatever that means. There's a lot of confusion between "CAP atomicity"==linearizability and "ACID atomicity"=="transactional atomicity"/"all or nothing"; see http://www.bailis.org/blog/hat-not-cap-introducing-highly-av...