Many of the elements below each constraint element PRO_E_DTMPLN_CONSTRAINT are used only for certain constraint types, so any given datum plane may contain fewer elements than are shown in the tree.

• 许多下面每个约束元素PRO_E_DTMPLN_CONSTRAINT只使用确定的约束类型，所以任何给定的基准平面可能包含比树里看到的少些的元素。