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CS 257 Database Systems Principles Assignment 1

This document explores the critical concept of information integration within database systems, highlighting three primary approaches: Federated Databases, Data Warehousing, and Mediators. It elaborates on the architecture of each approach, emphasizing how databases can effectively work together. It provides detailed examples involving car dealerships, illustrating one-to-one connections in federated systems, the transformation of local schemas to a global schema in data warehouses, and the role of mediators in facilitating virtual databases without maintaining their own data. Understanding these concepts is vital for effective database management and integration. ###

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CS 257 Database Systems Principles Assignment 1

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  1. CS 257Database Systems PrinciplesAssignment 1 Instructor:Student: Dr. T. Y. Lin RajanVyas (119)

  2. Modes of Information Integration

  3. Information • Information Integration allows database or other distributed information to work together. • Three most common approaches: • Federated Database • DataWareHousing • Mediators

  4. Federations • The simplest architecture for integrating several DBs • One to one connections between all pairs of DBs • n DBs talk to each other, n(n-1) wrappers are needed • Good when communications between DBs are limited

  5. Federated Database System • Sources are independent, but one source can call on others to supply information. • One-to-One connection between the all pairs of databases DB 1 DB 2 DB 3 DB 4

  6. Dealer 1 NeededCars(mode1, color, autotrans) • Dealer 2 Autos(seria1, model, color) Options(seria1, option) • Dealer 1 to Dealer 2 f or ( e a ch t u p l e (:m, : c , :a) in neededCars) if ( : a = TRUE) { /* automatic transmission wanted */ SELECT s e r i a l FROM Autos, Options WHERE Autos.seria1 = Options.seria1 AND Options.option = 'autoTrans' AND Autos.mode1 = :m AND Autos.color = :c; } e l s e { /* automatic transmission not wanted */ SELECT serial FROM Autos WHERE Autos.mode1 = :m AND Autos.color = :c AND NOT EXISTS ( SELECT * FROM Options WHERE s e r i a l = Autos.seria1 AND option = 'autoTrans' }; } } • Dealer 3 Cars(serialN0, model, color, autoTrans, ...)

  7. Data Warehouse • Sources are translated from their local schema to a global schema and copied to a central DB. • User transparent: user uses Data Warehouse just like an ordinary DB • User is not allowed to update Data Warehouse

  8. Information • Copies sources of data from several sources are stored in a single database. User Query Result Ware House Combiner Extractor 1 Extractor 2 Source 2 Source 1

  9. Example • Construct a data warehouse from sources DB of 2 car dealers: • Dealer-1’s schema: Cars(serialNo, model,color,autoTrans,cdPlayer,…) • Dealer-2’s schema: Auto(serial,model,color) Options(serial,option) • Warehouse’s schema: AutoWhse(serialNo,model,color,autoTrans,dealer) • Extractor --- Query to extract data from Dealer-1’s data: • INSERT INTO AutosWhse(serialNo, model, color, autoTans, dealer) • SELECT serialNo,model,color,autoTrans,’dealer1’ • From Cars;

  10. Extractor --- Query to extract data from Dealer-2’s data: • INSERT INTO AutosWhse(serialNo, model, color, autoTans, dealer) • SELECT serialNo,model,color,’yes’,’dealer2’ • FROM Autos,Options • WHERE Autos.serial=Options.serial AND option=‘autoTrans’; • INSERT INTO AutosWhse(serialNo, model, color, autoTans, dealer) • SELECT serialNo,model,color,’no’,’dealer2’ • FROM Autos • WHERE NOT EXISTS ( SELECT * FROM serial =Autos.serial AND option = ‘autoTrans’);

  11. Mediators

  12. It is a software component that supports a virtual database. • It stores no data of its own. User Query Result Mediator Wrapper Wrapper Source 2 Source 1

  13. Extractor for translating Dealer-2 data to the warehouse • INSERT INTO AutosWhse(serialNo, model, color,autoTrans, dealer) SELECT s e r i a l , model, color, ' y e s ' , 'dealer2' FROM Autos, Options WHERE Autos.seria1 = Options.seria1 AND option = 'autoTrans'; • INSERT INTO AutosWhse(serialNo, model, color,autoTrans, dealer) SELECT s e r i a l , model, color, 'no', 'dealer2‘ FROM Autos WHERE NOT EXISTS ( SELECT * FROM Options WHERE s e r i a l = Autos.seria1 AND option = 'autoTrans' );

  14. Thank You

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