jquery nested selects

nested.js

/**
 * 
 * usage: $('#select-container').nested({url:'/path/to/backend/which/returns/options/'})
 *
 */
(function($){
    $.fn.extend({ 
        //pass the options variable to the function
        nested: function(options) {
            //Set the default values
            var defaults = {
                url: '/',
                hide:true,
                empty:''
            }
            
            var options =  $.extend(defaults, options)
            
            var set_none = function(select) {
            	select.find('option[value=""]').attr('selected',true);
            }
            
            var set_disable = function(select) {
            	select.attr('disabled',true);
            }
            
            var clean = function(selects) {
            	selects.each(function(){
            		set_none($(this));
            		set_disable($(this));
            	})
            }
            
            var fill_select = function(next_select, data) {
            	var select = $(next_select);
            	var selected = select.find('option:selected');
            	select.find('option[value!=""]').not(selected).remove();
            	var options = '';
            	$.each(data, function(){
            		var value = this[0];
            		var text = this[1];
            		if (value==select.val()) {
            		    $.noop;
            		} else {
            		    options+='<option value="'+value+'">'+text+'</option>';
            		}
            	})
            	select.append($(options));
            }
            
            var get_options = function(name, id, next_select) {
            	if (id===options.empty) {
            		return;
            	}
            	$.post(options.url, {name:name, id:id}, function(data) {
            		fill_select(next_select, data);
            	}, "json");
            }
            
            var update = function(current_select, next_select) {
            	if (next_select==undefined) {
            		return false;
            	}
            	var name = $(current_select).attr('name');
            	var id = $(current_select).val();
            	get_options(name, id, next_select);
            }
            
            var initialize = function(selects) {
		    	selects.each(function(index){
		    		update($(this), selects.get(index+1));
		    	})
            }
            
	    	var redisable = function(selects) {
	    		var limit = false;
		    	selects.each(function(index){
		    		if (limit===true) {
		    			$(this).attr('disabled',true);
		    			set_none($(this));
		    			if (options.hide===true) {
            			    $(this).parent().fadeOut();
		    			}
		    		} else {
		    			$(this).attr('disabled',false);
		    			if (options.hide===true) {
            			    $(this).parent().fadeIn();
		    			}
		    		}
		    		value = $(this).val();
		    		if (value===options.empty) {
		    			limit = true;
		    		}
		    	})
	    	}
            
	    	var listen = function(selects) {
	    		selects.each(function(index){
	    			$(this).bind('change',function(){
                        update($(this), selects.get(index+1));
                        clean(selects.slice(index+1));
	    				redisable(selects);
	    			})
	    		})
	    	}
            
            return this.each(function() {
		    	var container = $(this);
		    	var selects = container.find('select');
		    	initialize(selects);
		    	redisable(selects);
		    	listen(selects);
            });
        }
	})
})
(jQuery);

How to integrate this plugin? Is it about select box inside another select box?