In addition to the above standard configuration elements, a third-party Java™ programmer may define its own custom configuration elements. Such elements are declared as follows:
... Any attributes here ...> ...
Any child nodes here... </com.acme.MyConfigElement>
The namespace of a custom configuration element is "
The local name of a custom configuration element is the fully qualified name of a Java™ class extending abstract class
The "Integrated spreadsheet engine" add-on makes use of such custom configuration elements. See Section 28, “Custom spreadsheet functions”.