A JEANMenuEnabler is java code that is called when the selection of nodes changes in either a Catalog or NodeList. During application-specific initialization a menu enabler can be applied to a specified menu item. The task of the menu enabler is to determine whether that menu item should be enabled for the given node selection. For example, an operation that can only be applied to a single item will be enabled if that is the current selection, or disabled if the selection involves more that one item, or a group or a category.