Changes

The most important thing to keep in mind when using XQuery Update is the Pending Update List (PUL). Updating statements are not executed immediately, but are first collected as update primitives within a set-like structure. At the end of a query, after some consistency checks, all update primitives on this list are applied in the following order:

If a conflict exists between the planned update operationsan inconsistency is found, an error message is returned and all accessed databases remain untouched (atomicity). For the user this means that updates are only visible '''after''' the end of a snapshot.