Upcoming SMW versions should have hooks that allow extensions to listen
to data changes. Through this, an extension could maintain its own
tables (or other backend) to be used for special tasks such as auto
We already have this since 1.6: hook SMWStore::updateDataBefore, which is used by Semantic Watchlist, which has such additional tables. You have to make your own diffs to see what changed though, which is what I guess you where referring to.
Jeroen De Dauw
Don't panic. Don't be evil.