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 Autonomy Logically Integrated Multiple DBMS Federated DBMS Multidatabase System low High  Transaction Control  Query Processing Distribution of Control Degree to which individual DBMS can operate independently

5 Characteristics-Distribution Deals with data Single DBS Many DBSs in a local area network Many DBSs in a wide area network Distribution Single DBS Multiple Sites 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 Loosely coupled Federated DBSNonfederated DBS Single FederationMultiple Federation Tightly coupled

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 Component DBS Local Schema Component Schema Export Schema Federated Schema External Schema Local Schema Component Schema Export Schema Federated Schema External Schema External Schema

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

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