As an important property of ORDBMS, inheritance provides powerful capability for incremental modeling of composite objects. It also makes the DSM (dynamic schem a modification) more complex. In this paper, the semantics of full inheritance i s subdivided, and a criterion model of DSM in ORDBMS is presented. With Inherita nce Hierarchy Selective Expression, the cascade strategy or migrate strategy use d on subclasses can be chosen freely when the schema of their super classes is m odified.