An extended entity-relationship model is discribed,and a simple entity-relationship model and a Canonical entity-relationship model are defined.
首先介绍了一个扩充实体-联系模型(EERM),定义了简单实体-联系模型(SERM)及规范实体-联系模型(CERM),然后给出了EERM到SERM,SERM到CERM的等价转换规则。
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