doctrine2/Doctrine/Identifier.php

<?php
class Doctrine_Identifier {
    /**
     * constant for auto_increment identifier
     */
    const AUTO_INCREMENT = 1;
    /**
     * constant for sequence identifier
     */
    const SEQUENCE       = 2;
    /**
     * constant for normal identifier
     */
    const NORMAL         = 3;
    /**
     * constant for composite identifier
     */
    const COMPOSITE      = 4;
}