1. A method comprising: receiving a query expression against a collection of XML documents stored in one or more database tables, wherein the collection of XML documents are stored based on a particular data storage format; determining that the query expression contains an updating expression that conforms to a language for querying XML documents, the updating expression specifying a particular operation for updating XML data; in response to determining that the query expression contains the updating expression that conforms to the language for querying XML documents, rewriting the query expression to form a first rewritten query expression comprising one or more path-based query operators, wherein the one or more path-based query operators are selected based on the particular operation for updating XML data specified by the updating expression; based on the particular data storage format storing the collection of XML documents, rewriting the first rewritten query expression to form a second rewritten query expression comprising one or more storage format specific query operators configured to update particular XML data of the collection of XML documents; and wherein the method is performed by one or more computing devices.