If an odbms ( object database management system ) is to be used , there is a direct mapping between structures in the class model and the odbms structure . this is not true for relational databases 如果使用物件资料库管理系统,类别模型结构和物件资料库管理系统结构之间应该可直接进行配对,但对于关系资料库而言则并不是这样。