题目内容
某公司需建立产品信息数据库，经调查其业务要求如下： Ⅰ．一种产品可以使用多个不同种类的部件，也可以使用多个不同种类的零件；一种部件至少被用在一种产品中；一种部件可以由多个不同种类的零件组成；一种零件至少被用在一种产品或一种部件中。 Ⅱ．对于一种具体的部件，要记录这种部件使用的各种零件的数量。 Ⅲ．对于一种具体的产品，要记录这种产品使用的各种部件数量和各种零件数量，但部件所使用的零件数量不计入该种产品的零件数量。 Ⅳ．一个供应商可供应多种零件，但一种零件只能由一个供应商供应。 根据以上业务要求，某建模人员构建了如下E-R图： 此E-R图中的实体的属性完整，但实体、联系的设计存在不合理之处。 请重新构建合理的E-R图，使之符合业务要求，且信息完整。
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