瞭解PowerDesigner的Logical Data Model

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).

我譯：不依賴於任何特殊的資料庫實現，邏輯資料模型（LDM）將幫助你分析一個資訊系統的結構。LDM移除了實體標識，並且沒有概念資料模型（CDM）抽象，也不允許你建立模型檢視，索引以及在更具體的PDM裡可以找到的物件。

問題：logical data model 被設計，它主要用來幹什麼？