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Database Design Slide 1

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  • 1. Database Systems Basic Concepts Dr. Ali H. El-Bastawissy Faculty of computers and Informatics Cairo University
  • 2. Unit01 Outlines • Types of Databases and Database Applications • Basic Definitions • Typical DBMS Functionality • Examples of a Database • Main Characteristics of the Database Approach • Database Users • Advantages of Using the Database Approach • When Not to Use Databases Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 2
  • 3. Definitions • Data: known facts that can be recorded • Database: a collection of data • represents some aspect of the real world • logically coherent collection (not a random collection) • designed, built & populated for a specific purpose • Database Management System: the software that manages the data Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 3
  • 4. Database Systems Data Definition Payroll Schedules Grades • Data Integrity, Data definition, DBMS Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 4
  • 5. Characteristics of the Database Approach • insulation of programs & data • support of multiple user views • use of a catalog to support database descriptions DB A collection of described and interrelated data stored and managed by general purpose DBMS Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 5
  • 6. DBMS Functions • Data Dictionary • Data Storage Management • Data Transformation and Presentation • Security • Multi-user Access Control • Backup and Recovery • Data Integrity • Database Access Language • Database Communication Interface Dr. Ali El-Bastawissy 2007 DB01: Introduction to DB Slide 6
  • 7. Database System Environment Users/Programmers Database Application Programs/Queries System DBMS Software Software: Query Processing & Programs Software: Data Access Database Database Definition Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 7
  • 8. Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 8
  • 9. Database Players • DBA – access authorization, coordination & monitoring database usage, problem determination, performance tuning etc • Designers – identify the requirements & chose the appropriate structures to represent & store the data • Users (Casual, parametric, Sophisticated, stand-alone) • System analysts & application programmers • DBMS system designers & implementers • Tool developers • Operators & maintenance personnel Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 9
  • 10. DBMS Interfaces • Menu-based Interfaces for browsing • Forms-based Interfaces • GUIs • Natural Language Interfaces • Specialized Interfaces • Interfaces for the DBA • Query Language Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 10
  • 11. Classification of DBMSs • Data Model Classification – relational, network, hierarchical, object-oriented • Number of users – single user or multi-user • Number of Sites – centralized vs distributed • Cost of the DBMS Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 11
  • 12. Areas of Database Study • DBMS software • Database Design • Query Languages • Application Programming • Database Administration • Data Warehousing & Data Mining Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 12
  • 13. When not to use a DBMS • Costs of using a DBMS: – High initial investment and possible need for additional hardware. – Overhead for providing generality, security, concurrency control, recovery, and integrity functions. • When a DBMS may be unnecessary: – If the database and applications are simple, well defined, and not expected to change. – If there are stringent real-time requirements that may not be met because of DBMS overhead. – If access to data by multiple users is not required. Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 13
  • 14. When not to use a DBMS • When no DBMS may suffice: – If the database system is not able to handle the complexity of data because of modeling limitations – If the database users need special operations not supported by the DBMS. Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 14
  • 15. Data Model • A collection of concepts that can be used to define the DB structure (data items& types, relationships, operations|behavior, and constraints). • Some Data Models: – Entity Relationship model – Relational Model – hierarchical & network models – object-data models Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 15
  • 16. Conceptual Models Entities, attributes & relationships Categories of Data Models Implementation Models Record Structures Physical Record formats, Models record orderings, access paths Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 16
  • 17. Categories of Data Models • Conceptual (high-level, semantic) data models: – Provide concepts that are close to the way many users perceive data. • (Also called entity-based or object-based data models.) • Physical (low-level, internal) data models: – Provide concepts that describe details of how data is stored in the computer. These are usually specified in an ad-hoc manner through DBMS design and administration manuals • Implementation (representational) data models: – Provide concepts that fall between the above two, used by many commercial DBMS implementations (e.g. relational data models used in many commercial systems). Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 17
  • 18. Three-Schema Architecture External External External View #1 View #2 ... View #n mapping Conceptual Schema mapping Internal Schema Stored database Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 18
  • 19. Three-Schema Architecture • Defines DBMS schemas at three levels: – Internal schema at the internal level to describe physical storage structures and access paths (e.g indexes). • Typically uses a physical data model. – Conceptual schema at the conceptual level to describe the structure and constraints for the whole database for a community of users. • Uses a conceptual or an implementation data model. – External schemas at the external level to describe the various user views. • Usually uses the same data model as the conceptual schema. Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 19
  • 20. Three-Schema Architecture • Mappings among schema levels are needed to transform requests and data. – Programs refer to an external schema, and are mapped by the DBMS to the internal schema for execution. – Data extracted from the internal DBMS level is reformatted to match the user’s external view (e.g. formatting the results of an SQL query for display in a Web page) Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 20
  • 21. Data Independence • Logical data independence - ability to change the conceptual schema without having to change the external schemas or application programs • Physical data independence - ability to change the internal schema without having to change the conceptual (or external) schemas. Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 21
  • 22. DBMS Languages • DDL: Data Definition Language – used to define/change the structure of the database (SDDL, CDDL, VDDL) • DML: Data Manipulation Language – used to query the database, insert data, change data or delete data (Nonprocedural|procedural (embedded) DML) (set-at-a-time |record-at-a-time DML) Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 22
  • 23. DBMS Architectures • Centralized DBMS: – Combines everything into single system including- DBMS software, hardware, application programs, and user interface processing software. – User can still connect through a remote terminal – however, all processing is done at centralized site. Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 23
  • 24. DBMS Architectures Basic 2-tier Client-Server Architectures • Specialized Servers with Specialized functions – Print server – File server – DBMS server – Web server – Email server • Clients can access the specialized servers as needed Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 24
  • 25. Logical two-tier client server architecture Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 25
  • 26. Clients • Provide appropriate interfaces through a client software module to access and utilize the various server resources. • Clients may be diskless machines or PCs or Workstations with disks with only the client software installed. • Connected to the servers via some form of a network. – (LAN: local area network, wireless network, etc.) Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 26
  • 27. DBMS Server • Provides database query and transaction services to the clients • Relational DBMS servers are often called SQL servers, query servers, or transaction servers • Applications running on clients utilize an Application Program Interface (API) to access server databases via standard interface such as: – ODBC: Open Database Connectivity standard – JDBC: for Java programming access • Client and server must install appropriate client module and server module software for ODBC or JDBC Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 27
  • 28. DBMS Architectures Three Tier Client-Server Architecture • Common for Web applications • Intermediate Layer called Application Server or Web Server: – Stores the web connectivity software and the business logic part of the application used to access the corresponding data from the database server – Acts like a conduit for sending partially processed data between the database server and the client. • Three-tier Architecture Can Enhance Security: – Database server only accessible via middle tier – Clients cannot directly access database server Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 28
  • 29. Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 29
  • 30. Summary • Types of Databases and Database Applications • Basic Definitions • Typical DBMS Functionality • Examples of a Database • Main Characteristics of the Database Approach • Database Users • Advantages of Using the Database Approach • When Not to Use Databases Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 30
  • 31. Summary • Data Models and Their Categories • History of Data Models • Schemas, Instances, and States • Three-Schema Architecture • Data Independence • DBMS Languages and Interfaces • Classification of DBMSs • Database System Utilities and Tools • Centralized and Client-Server Architectures Dr. Ali El-Bastawissy DB01: Introduction to DB Slide 31
  • 32. DB Unit 01 Intro Finish Line Questions Dr. Ali H. El-Bastawissy Faculty of computers and Informatics Cairo University

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