Download
1 / 24
240 likes | 431 Vues
Temporal Database. Chap 4: Temporal Extensions to the Relational Model and SQL. 4.2 Temporal Relational Model (TRM). 4.2 Temporal Relational Model (TRM). 4.2.1 Synchronism and Temporal Dependence.
E N D
Temporal Database Chap 4: Temporal Extensions to the Relational Model and SQL
4.2.1 Synchronism and Temporal Dependence Here, an Employee gets a raise in salary if and only if he or she gets a promotion, and an employee is never demoted. Thus, the TVA’s Salary and Position form a set of synchronous attributes .
4.2.1 Synchronism and Temporal Dependence Plane# is the identifier of an aircraft, Part is the name of a part, Cond describes the nature of the problem the part has, Place is the name of the place where it is being serviced, Cost is the cost associated with the Ts is the time when a particular maintenance event began , and TE is the time when it terminated.
4.2.2 Time Normalization Sal-Mgr (Table 4.3) can be decomposed into two relations, Manager (Table 4.4) and Salary (Table 4.5)
4.3.3 Temporal Ordering If there are n breaks for a given TIK value, then the tuples can be viewed as having been partitioned into n+1 groups. If breaks are taken into consideration for temporal ordering, the tuples in each of these groups created by the presence of breaks – are given a unique set of ordinal numbers.
