XQuery Updates implementation

It is now possible to use the copy-modify expression without explicitly configuring Saxon to use a mutable tree model such as the linked tree. The linked tree will automatically be used for the temporary tree constructed by the copy-modify expression.

The fn:put() function now takes account of serialization parameters set within the query body using declarations such as declare option output:indent "yes". (It does not, however, take account of serialization parameters set on the command line.)