Chapter 4 Building Conceptual Data Models
An identifier is an entity attribute, or a combination of entity attributes, whose values uniquely identify each occurrence of the entity. An identifier is the CDM equivalent of a primary key or an alternate key in a physical data model (PDM).
Each entity must have at least one identifier. If an entity has only one identifier, it is designated by default as the primary identifier for the entity. A primary identifier is the main identifier for an entity.
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