1.4.31. Do you provide the ability to atomically add a set of triples, where either all are added or none are added?

Yes. Doing this with millions of triples per transaction may run out of rollback space. Also, there is risk of deadlock if multiple such inserts run at the same time. For good concurrency, the inserts should be of moderate size. As usual, deadlocks are resolved by aborting one of the conflicting transactions.