1.1.8 Understanding Identifying Attributes

Here are some other important points to remember when working with identifying attributes of an object.

Identifying Attribute Rules:

• An entity does not have to have an identifying attribute.  In some instances, an entity may be identified solely by its parents or may not require any identification.

• An entity may have only one identifying or key attribute.  It is important to note that more attributes may be required to uniquely identify an occurrence within the entity, i.e. you require the parent keys along with the identifying attribute.

• If an entity has more than one parent, it does not require an identifying attribute. The two parent keys will identify the child entity.  For example, a Customer is the parent of Customer Products and Product is the parent of Customer Products. Customer Products is an entity listing which customers have which products.

• Parent keys are compounded. A parent key may be made up of more than one attribute.  For example, a Company is a parent of a Department which is a parent of Employee. Employee has two parent keys: Company Code and Department Code.