To be effective, it must be simple enough to communicate the required data structure to the end user, yet detailed enough that the database designer can create the physical structure.

• 为了是资料模型更加有效,它必须足够简单以使最终用户能够沟通必需的资料结构,同时它也要足够详细以使资料库设计人员能够建立物理结构。