Attribute Types The set of allowed values for each attribute is called the domain of the attribute Attribute values are(normally)required to be atomic;that is, indivisible The special value null is a member of every domain.Indicated that the value is "unknown The null value causes complications in the definition of many operations Database System Concepts-6th Edition 2.3 @Silberschatz,Korth and SudarshanDatabase System Concepts - 6 2.3 ©Silberschatz, Korth and Sudarshan th Edition Attribute Types The set of allowed values for each attribute is called the domain of the attribute Attribute values are (normally) required to be atomic; that is, indivisible The special value null is a member of every domain. Indicated that the value is “unknown” The null value causes complications in the definition of many operations