A specialized visitor base class that can be used for storing the tree of configuration nodes. The basic idea is that each node can be associated with a reference object. This reference object has a concrete meaning in a derived class, e.g. an entry in a JNDI context or an XML element. When the configuration tree is set up, the load() method is responsible for setting the reference objects. When the configuration tree is later modified, new nodes do not have a defined reference object. This visitor class processes all nodes and finds the ones without a defined reference object. For those nodes the insert() method is called, which must be defined in concrete sub classes. This method can perform all steps to integrate the new node into the original structure.