Attribute

Attributes are properties used to describe an entity, a specific entity will have a value for each of its attributes. Each attribute has a value set (data type) associated with it, e.g. integer, string, date, etc.

Types of attributes:

• Simple attribute

  Simple attribute: each entity has an atomic value for this attribute. Example: ID

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• Composite attribute

  Composite attribute: the attribute may be composed of several components, it may form a hierarchy where some components are themselves composite. Example: Name(First, Middle, Last)

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• Single-valued attribute

  Single-valued attribute: each entity can have a single value for this attribute. Example: Age attribute for each Person.

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• Multi-valued attribute

  Multi-valued attribute: an entity may have multiple values for this attribute. Example: Current Courses of a STUDENT.

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  An attribute may be both composite and multi-valued.