### Attribute Types and Instances

Each attribute type definition in the schema consists of attribute type identifiers (UUID and name) and semantics that control the instances of attributes of this type. In this manual, schema entry refers to the registry entry that defines an attribute type.

An attribute instance is an attribute that is attached to an object and has a value (as opposed to an attribute type, which has no values but simply defines the semantics to which attribute instances of that attribute type must adhere). Attribute instances contain the UUID of their attribute type.

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