contact.php

<?php 
class Contact extends AppModel {
	var $actsAs = array('Acl' => array('requester'));
	var $belongsTo = array(
		'Account', 
		'Role',
		'Supervisor' => array(
			'className' => 'Contact',
			'foreignKey' => 'supervisor_id'
		)
	);
	var $displayField = 'abbr_name';
	var $hasMany = array(
		'Notice' => array('foreignKey' => 'contact_id'),
		'Document' => array('foreignKey' => 'created_by')
	);		
	var $_findMethods = array('accessible' => true, 'roles' => true);

	function __construct($id = false, $table = null, $ds = null) {	
		parent::__construct($id, $table, $ds);
		
		$this->virtualFields = array(
			'full_name' => "CONCAT(`{$this->alias}`.`first_name`, ' ', `{$this->alias}`.`last_name`)",
			'directory_name' => "CONCAT(`{$this->alias}`.`last_name`, ', ', `{$this->alias}`.`first_name`)",
			'abbr_name' => "CONCAT(LEFT(`{$this->alias}`.`first_name`, 1), '. ', `{$this->alias}`.`last_name`)"
		);	
	}

user_trackable.php

<?php
class UserTrackableBehavior extends ModelBehavior {
	function setup(&$model, $settings = array()) {
		$this->settings[$model->alias] = array_merge(array('userModel' => 'User'), $settings);
		
		# Initialize user model
		if (empty($this->userModel[$model->alias])) {
			$this->userModel[$model->alias] =& ClassRegistry::init($this->settings[$model->alias]['userModel']);
		}
		
		# Cache user ids for translation
		if (empty($this->userList[$this->settings[$model->alias]['userModel']])) {
			$this->userList[$this->settings[$model->alias]['userModel']] = $this->userModel[$model->alias]->find('list', array('callbacks' => false));
		}	
	}