XQuery Update Facility
The XQuery 1.0 language provides expressions for querying input documents and adding to the results. However, it does not have any specific expressions for inserting, updating, or deleting XML data. As we saw in Chapter 9, it is possible to modify input elements and attributes using user-defined functions, but this is somewhat cumbersome. In addition, this only transforms input documents to be returned as the query results; it offers no ability to specify that XML data should be permanently changed in a database.
To address this need, the W3C XQuery Working Group is working on an XQuery Update Facility that will provide specialized operators and/or built-in functions for updates. At the time of this writing, only a draft requirements document has been publicly released. It specifies that the XQuery Update Facility will have functionality that allows for:
Deleting nodes
Inserting nodes in specified positions
Replacing nodes
Moving nodes
Changing the typed value of nodes
Modifying properties of a node, such as name, type, content, base URI, etc.
For more information on the XQuery Update Facility requirements, see http://www.w3.org/TR/xquery-update-requirements.
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