Rule 7 of upd:applyUpdates() states "The upd:applyUpdates operation is atomic with respect to the data model. In other words, if upd:applyUpdates terminates normally, the resulting XDM instance reflects the result of all update primitives; but if upd:applyUpdates raises an error, the resulting XDM instance reflects no changes. "

I believe this is untestable and therefore doesn't belong in the spec. It's also very unclear what requirements it is placing on the implementation. Does it mean, for example, that streamed delivery of updated XDM instances is not allowed unless such streamed delivery is guaranteed to succeed? I can't see any reason for placing such an onerous requirement. But if it doesn't mean that, what does it mean? Does it mean that implementations are required to make the original un-updated XDM instance available to the application after an error? That would be a strange requirement to impose, given that we say nothing about how updated instances are made available to applications in the success case. Perhaps it means that persistent data should be unchanged in the event of a dynamic error? But handling of persistent data is explicitly out of scope!