The developer's guide mentions the classpath requirements for using the XML operators: http://db.apache.org/derby/docs/dev/devguide/cdevstandardsxml.html
DERBY-2739, this section is a bit out of date and the following should be updated:
1) "For the XML operators to work properly, Derby requires that a JAXP parser, such as Apache Xerces, and Apache Xalan are included in the Java classpath."
Since we're no longer using Xalan directly, we shouldn't state that Apache Xalan must be in the classpath. We could for example replace "Apache Xalan" in the above sentence with "and a DOM Level 3 XPath implementation, such as Apache Xalan,".
2) "After JVM version 1.4, Sun renamed the JAXP packages. Derby cannot find these renamed packages."
This is no longer true. Derby can now find the required packages on newer Sun JVMs (at least on Java 6 and newer).