Client-centric consistency

Causal Consistencyは以下の4つのConsistencyを保証する

table:分類

先\後 Read Write

定義

If a process reads the value of a data item x, any successive read operation on x by that process will always return that same value or a more recent value.

A write operation by a process on a data item x is completed before any successive write operation on x by the same process.

同じプロセスによるwriteは、順番が入れ替わってはダメ。並行でもダメ。

The effect of a write operation by a process on data item x will always be seen by a successive read operation on x by the same process

同じプロセスによるwriteは、それ以降のreadから読めないといけない

A write operation by a process on a data item x following a previous read operation on x by the same process is guaranteed to take place on the same or a more recent value of x that was read

writeは、それ以前に同じプロセスによってreadされた値もしくはそれより新しい値を書き換えるような命令でないといけない