1 Spring 2000 Christophides Vassilis FROM RELATIONAL TO OBJECT DATABASE MANAGEMENT SYSTEMS V. CHRISTOPHIDES Department of Computer Science & Engineering University of California, San Diego ICS - FORTH, Heraklion, Crete

2 Spring 2000 Christophides Vassilis I) INTRODUCTION

3 Spring 2000 Christophides Vassilis What is a DBMS? l Database: Logically coherent collection of “computerized” data u Stored Data: Persistent facts with some inherent meaning u Accessible Data: Extracted and derived facts for a specific purpose l Database Management System: General purpose software that facilitates the process of defining, constructing and manipulating database for various applications. It offers the following services: u Data Persistence u Disk Management u Data Sharing u Data Reliability u Ad hoc Queries

4 Spring 2000 Christophides Vassilis DBMS Applications l Administration & Management u Bank Accounts u Company Stocks & Personal u Airline Reservation u University Courses and Notes u Library Books Borrowing l Media & Net-centric Applications u Engineering (CAD/CAM/CIM/CAE) u Scientific Applications  Genome Databases, Environmental Applications (GIS) u Telecommunications + Databases  Network management, Tele- medicine, Info Brokering u Multimedia, Entertain., Visualization  Interactive, Virtual Reality based u Software Design and Management u Data Warehouses u Web Site Management u Electronic Commerce

5 Spring 2000 Christophides Vassilis DBMS vs. other types of software l Effective Manipulation of Persistent Data u recovery from failures u concurrent access u security & integrity controls u data independence physical & logical & user l Efficient Access to Large Data Volumes u buffer management u indexing/clustering u query optimization u distribution

6 Spring 2000 Christophides Vassilis Example: Phone Directory l One file:  first and last name, address, profession, telephone number l Two type of access:  Direct by first/last name (white pages)  Sequential by profession headings (yellow pages) l Implementation without a DBMS:  Hashing on first/last name (key) and linked lists of profession headings  Change of the access mode implies PROGRAM RERWITING l Implementation with a DBMS:  Choice of a physical structure  Choice of a logical structure  Application programs are build on the top of data logical structuring

7 Spring 2000 Christophides Vassilis The ANSI-SPARC Architecture l External Level: u What actually seen by users (not necessary the whole database) l Conceptual Level: u Modeling of the real-word data, independent from the underlying DBMS l Internal Level: How data is physically stored u Logical-schema: Logical organization of data using the DBMS data model (tables, etc.) u Physical-schema: Physical organization of data in the secondary memory (files, records, etc.) òThe ability to modify a scheme definition in one level without affecting a scheme definition in a higher level is called data independence

8 Spring 2000 Christophides Vassilis Three Level Architecture PHYSICAL SCHEMA LOGICAL SCHEMA INTERNAL LEVEL CONCEPTUAL LEVEL EXTERNAL LEVEL VIEW 1VIEW 2VIEW 3 INTEGRATION

9 Spring 2000 Christophides Vassilis The Data Independence issue l Physical (for optimization)  Changes of physical structures doesn’t affect data logical organization  EXAMPLE: Addition/Suppression of indices in a DBMS l Logical (for maintainability)  Modifications of data logical structure should not affect programs  EXAMPLE: New Relations/Attributes in the logical schema of a DBMS l User (for flexibility)  Multiple views on the same logical organization of data  EXAMPLE: Secretary and Professor views on a University database 4Data independence is achieved by inter-level mappings 4Queries are translated between levels automatically

10 Spring 2000 Christophides Vassilis Mappings in DBMS

11 Spring 2000 Christophides Vassilis DBMS Components l Data Collections:  Minimizing data redundancy  Enabling multi-user access l People:  Database Designer  Database Administrator  Application Programmers  End-Users l Hardware:  Processor(s)  Main Memory  Secondary Storage (e.g., disks, CD-ROMs, etc.) l Software  The Storage Manager: buffer and file manager  The Transaction Manager: locking, logging, and transaction commitment (ACID)  The Query Processor: parsing, optimization, execution  Various Automated Tools: Development and Design aids, Report writers, etc.

12 Spring 2000 Christophides Vassilis Typical Architecture of a DBMS Schema Modifications Data Modifications Queries “Query” Processor Storage Manager Transaction Manager Data & Metadata

13 Spring 2000 Christophides Vassilis Application Development: Backend vs. Frontend l Backend  the DBMS l Frontends  Applications which run on top of the DBMS l Examples of vendor-provided applications or tools  Query language processor  Business graphics sub-systems  Spreadsheet  Statistical packages  Application generators  CASE Tools  Report writer  Web-DBMS Gateways l Examples of typical utilities to help DBAs in various tasks  Load routines  Unload/Reload routines  Reorganization routines  Statistic routines  Analysis routines

14 Spring 2000 Christophides Vassilis Application Development: Client/Server Architecture l Partition of programs between client et server processes, communicating via queries l Hierarchical partition of functions u data at the servers are shared by several clients u graphical interfaces at the end- user workstations u communication through standardized protocols u distribution of application programs in order to minimize transfer costs

15 Spring 2000 Christophides Vassilis Client/Server Architecture: First Generation Windows NTUNIX CLIENTS APPLICATIONS Queries Results rules DBMS NT, UNIX, NOVELL GCOS, VMS, MVS APPLICATIONS SERVER APPLICATION Data  G. Gardarin

16 Spring 2000 Christophides Vassilis Client/Server Architecture: Second Generation Application Application Tool Connectivity Tool Network Protocol DB Server Database CLIENTS Service Requests Results SERVER Network Protocol Connectivity Tool Stored Procedures l Stored Procedures u Procedure accomplice a service function on data l Service-oriented architecture rather than query-oriented u Distribution of data manipulation l Extensibility and Scalability u Possibility to have several, eventually redundant, servers u Possibility to have private data on clients Application Application Tool Connectivity Tool Network Protocol Service Requests  G. Gardarin

17 Spring 2000 Christophides Vassilis Client/Server Architecture: Third Generation l Integration of the Web with the client-server u Use Web browsers for a standard presentation to the client u Possibility to run small client application (applets) u Significant portability (Virtual Private Network, Intranet, Internet) l Three(or Multi)-tiered Architectures u Databases with stored procedures u Shared application services l Hypermedia support u Various media types which can be extended (text, image, video) u Navigation between documents and applications OracleDatabase URL HTML WRB WRB WRB WRB WRB Web Request Broker Cartridges Web Request Broker HTTP Server Files or CGI PL/SQL C Java Perl JCORBA Browser  ORACLE

18 Spring 2000 Christophides Vassilis Database Technology Timeline Early 80sLate 80sEarly - Mid 90s Late 90s - 21st C Pre- relational Early Relational Client-server Relational Enterprise -capable Relational Internet Computing Simple OLTP Active Database Data Warehouse & Hi-end OLTP Packaged & Vertical Applications Simple transactions, on-line backup & recovery Stored procedures, triggers Scaleable OLTP, parallel query, partitioning, cluster support, row-level locking, high availability Middleware (messaging, queues,events) Java, CORBA, Web interfaces Support for all types of data, extensibility, objects Simple Data Management Global Enterprise Management