In UML models, enumerations are model elements that represent user-defined data types. Enumerations contain sets of named identifiers, called enumeration literals, that represent the values of the enumeration. Enumerations can represent primitive types, such as integer and Boolean types, or user-defined types. In a profile, you can specify an enumeration as the type for an attribute. For example, you can specify an enumeration called Days and an enumeration literal for each day of the week. You can then create an attribute called MyFavoriteDay of type Days and specify the enumeration literal called Saturday as the default value for the attribute.