By Paul Murray Claire McQuade Kashif Rafiq David Miller

1. By Paul Murray Claire McQuade Kashif Rafiq David Miller

2. Introduction • Federated Databases (FDBSs) • Key areas • Characteristics of DBS/FDBS • Architecture • Views

3. Characteristics - of DBS • Distribution • Autonomy • Heterogeneity

4. Characteristics - Autonomy • Transaction Control • Query Processing • Distribution of ControlDegree to which individual DBMS can operate independently Logically Integrated Multiple DBMS Multidatabase System Federated DBMS Autonomy low High

5. Characteristics-Distribution • Deals with data • Single DBS • Many DBSs in a local area network • Many DBSs in a wide area network Multiple Sites Single DBS Distribution Local Distributed

6. Characteristics-Distribution • Data and the Federated Database System (FDS) • Databases may be on the same computer • Databases may be geographically separate • Systems must be able to communicate • Benefits of distribution • Improved access times • Improved availability • Improved reliability

7. Characteristics -Heterogeneity • Data models • Structures • Constraints • Query languages

8. Characteristics of FDBS • Collection of cooperating but autonomous component database systems (DBSs) • Component DBSs integrated to various degrees • FDBMS • Software that provides controlled and coordinated manipulation of the component DBSs • No centralized control

9. Types of FDBS Multidatabase System Nonfederated DBS Federated DBS Loosely coupled Tightly coupled Single Federation Multiple Federation

10. Components of FDBS

11. Architecture • Processor • Coupling • Schemas

12. Architecture - Processor • Transforming Processors • Filtering Processors • Constructing Processors • Accessing Processors

13. Transforming Processors

14. Filtering Processors

15. Constructing Processors

16. Accessing Processors

17. Architecture - Coupling • Loosely Coupled FDBS • Tightly Coupled FDBS

18. Architecture - Schema • Schema Models • Five layer model • Seven layer model • Schema evolution

19. Schema - Five-Level External Schema External Schema External Schema Federated Schema Federated Schema Export Schema Export Schema Export Schema Component Schema Component Schema Local Schema Local Schema Component DBS Component DBS

20. Schema-Five-Level Processor External Schema External Schema Filtering Processor Filtering Processor Federated Schema Federated Schema Constructing Processor Constructing Processor Export Schema Export Schema Filtering Processor Filtering Processor Component Schema Component Schema Transforming Processor Transforming Processor Local Schema Local Schema Component DBS Component DBS

21. Schema - Evolution • One of the problems found with federated databases is the cumulative schema evolution rate • A client application cannot be tied to a specific integrated view of the federation, as all it takes is one member of the federation to change its schema without ensuring backward compatibility to cause serious problems

22. Semantic - Integrity Constraints • The federated database schema should correctly reflect the semantics of the component database schemata of which it is composed • Since the semantics of a database schema is also determined by a set of semantic integrity constraints, a correct schema integration has to deal with integrity constraints existing in the different component database schemata

23. Architecture - Views • Selection • Projection • Join • Real

24. Conclusion