DBTG Sets The structure consisting of two record types that are linked together is referred to in the DBTG model as a DBTG set In each DBTG set,one record type is designated as the owner,and the other is designated as the member,of the set. Each DBTG set can have any number of set occurrences(actual instances of linked records). Since many-to-many links are disallowed,each set occurrence has precisely one owner,and has zero or more member records. No member record of a set can participate in more than one occurrence of the set at any point. A member record can participate simultaneously in several set occurrences of different DBTG sets Database System Concepts,5th Ed. A.9 ©Silberschat乜，Korth and SudarshanDatabase System Concepts, 5 A.9 ©Silberschatz, Korth and Sudarshan th Ed. DBTG Sets The structure consisting of two record types that are linked together is referred to in the DBTG model as a DBTG set In each DBTG set, one record type is designated as the owner, and the other is designated as the member, of the set. Each DBTG set can have any number of set occurrences (actual instances of linked records). Since many-to-many links are disallowed, each set occurrence has precisely one owner, and has zero or more member records. No member record of a set can participate in more than one occurrence of the set at any point. A member record can participate simultaneously in several set occurrences of different DBTG sets