A logical data model (LDM) helps you analyze the structure of an information system, independent of any specific physical database implementation. An LDM has migrated entity identifiers and is less abstract than a conceptual data model (CDM), but does not allow you to model views, indexes and other elements that are available in the more concrete physical data model (PDM).

我译:不依赖于任何特殊的数据库实现,逻辑数据模型(LDM)将帮助你分析一个信息系统的结构。LDM移除了实体标识,并且没有概念数据模型(CDM)抽象,也不允许你创建模型视图,索引以及在更具体的PDM里可以找到的对象

问题:logical data model 被设计,它主要用来干什么?