inheritance - Doctrine 2 多重レベル継承

Question

複数レベルの継承に問題があります

/**
 * @ORM\Entity
 * @ORM\Table(name="et_date")
 * @ORM\InheritanceType("JOINED")
 * @ORM\DiscriminatorColumn(name="type", type="string")
 * @ORM\DiscriminatorMap({"Relative" = "DateRelative", "Absolue" = "DateAbsolue"})
 */
class Date {}

/**
 * @ORM\Entity
 * @ORM\Table(name="et_date_absolue")
 */
class DateAbsolue extends Date{}

/**
 * @ORM\Entity
 * @ORM\Table(name="et_date_relative")
 * @ORM\InheritanceType("SINGLE_TABLE")
 * @ORM\DiscriminatorColumn(name="type", type="string")
 * @ORM\DiscriminatorMap({"Inscription" = "DateRelativeInscription", "Devoir" = "DateRelativeDevoir"})
 */
class DateRelative extends Date {}

/**
 * @ORM\Entity
 * @ORM\Table(name="et_date_relative_inscription")
 */
class DateRelativeInscription extends DateRelative{}

DateRelative エンティティの識別子列が存在しません...