#include <DbXml.hpp>

class DbXml::XmlExternalFunction {
public:
    virtual XmlResults execute(XmlTransaction &txn, 
                               XmlManager &mgr, 
                               const XmlArguments &args) const;
    virtual void close();
}; 

The XmlExternalFunction class is used to implement XQuery extension functions in C++. An implementor creates a subclass of XmlExternalFunction and returns an instance of the class from XmlResolver::resolveExternalFunction. Returned instances may be singleton objects which means the application must eventually free the memory, or new instances in which case the instance should delete itself in its XmlExternalFunction::close() method.