1. 1 ICS 214B: Transaction Processing and Distributed Data Management Lecture 16: Heterogeneous Distributed Databases Professor Chen Li

2. ICS214BNotes 162 Heterogeneous DB systems Federated DB systems Multi-DB systems Integration DB

3. ICS214BNotes 163 Multi-database systems Heterogeneity caused by autonomy –Different departments, companies, schools… Sources of heterogeneity  Data model  Query language  Schema  Transaction Processing Autonomous execution

4. ICS214BNotes 164 GUI MDBMS (Mediator) GS DBMS 1 DBMS 2 DBMS n... U1U1 U2U2 UnUn D2S2D1S1DnSn

5. ICS214BNotes 165 Interoperability Schema integration Query Processing Transaction Processing

6. ICS214BNotes 166 Global schema T 1 T 2 T n S1S1 S2S2 SnSn... InS1InS1 InS2InS2 InSnInSn Integrator GS

7. ICS214BNotes 167 Example: S 1 : relational E (ENO, ENAME, TITLE) D (DNO, DNAME) W (ENO, DNO) S (TITLE, SALARY) DNO, Dname ENO, ENAME, TITLE Salary Hypergraph representation E D W S

8. ICS214BNotes 168 S 2 : Object Oriented DEPT EMPLOYS ENGR DEPT-NAMEBUDGETMGR NAMEADDRESSTITLESALARYE#

9. ICS214BNotes 169 ER model for S 1 : NMNM W DE DNOENOENAME TITLESALARY DNAME

10. ICS214BNotes 1610 Or maybe? W DE DNOENOENAME TITLE SALARY DNAME S pay

11. ICS214BNotes 1611 ER model for S 2 Y DEPTENGR DEPT-NAMEE#NAME TITLE SALARY BUDGET N1 MGRADDR

12. ICS214BNotes 1612 DEPT INTEGRATION: D DEPT-NAME DNO DNAME BUDGETMGR D S1 S2

13. ICS214BNotes 1613 D DEPT-NAME BUDGETMGRNICKNAME DNO D DEPT-NAME DNO DNAME BUDGETMGR D

14. ICS214BNotes 1614 EMPLOYEE INTEGRATION: ENGRE NAMEENOENAME TITLE E# SALARY TITLE SALARY ADDR

15. ICS214BNotes 1615 ENGRE ENOENAME SALARY TITLE ADDR subset ENGRE NAMEENOENAME TITLE E# SALARY TITLE SALARY ADDR

16. ICS214BNotes 1616 One issue: matching attributes Another issue: matching values Example: Salary at A is weekly in dollars Salary at B is monthly in pounds Salary at C is Rate  hours-worked

17. ICS214BNotes 1617 Works-in relationship: N M N 1 ED W ED W

18. ICS214BNotes 1618 One option: N M ED W

19. ICS214BNotes 1619 Another option: ED works in pays NM 1 N

20. ICS214BNotes 1620 Query processing Query Subquery 1 … Subquery n

21. ICS214BNotes 1621 Example Site 1 DNO NICKNAME ( DNAME ) Site 2 DEPT_NAME BUDGET MGR Site 3: DNO DEPT_NAME D DEPT-NAME BUDGET MGRNICKNAME DNO

22. ICS214BNotes 1622 Find nickname & budget for DNO=55 Site 1: find nickname for DNO=55 Site 3: find dept_name for DNO=55   Site 2: find budget for dept_name= 

23. ICS214BNotes 1623 Example Find ENO, SALARY for TITLE =  ENGRE ENOENAME SALARY TITLE ADDR

24. ICS214BNotes 1624 Site 1: find E(ENO, SALARY) for TITLE =  Site 2: find ENGR(E#, SALARY) for TITLE =  Assume the salaries are consistent

25. ICS214BNotes 1625 Updates Update GS u 1 u 2 u n...

26. ICS214BNotes 1626 May be hard Example: ENAME in S 1 is 10 bytes ENAME in S 2 is 20 bytes ENAME in GS is 20 bytes Insert ENAME = “Smith”

27. ICS214BNotes 1627 Typically Updates done using local schemas

28. ICS214BNotes 1628 Query Optimization At each site: Different statistics Different algorithms for Q.P. Different exported functionality

29. ICS214BNotes 1629 In heterogeneous DBMS: –Integration –Query Processing/Optimization is an art…  VERY HARD 