Database Systems - Lec 1: Database System Concepts and Architecture - Nguyen Thanh Tung

Nội dung text: Database Systems - Lec 1: Database System Concepts and Architecture - Nguyen Thanh Tung

1. Outline ▪ File-based Approach ▪ Database Approach • Database Systems • Roles in the Database Environment • DBMSs ▪ Three-Schema Architecture and Data Independence ▪ Database Languages ▪ Data Models, Database Schema and Database State ▪ Data Management Systems Framework • Where are we? • Extending database capabilities for new applications ▪ Reading Suggestion: • [1,2]: Chapters 1, 2 ) 2
2. File-based Approach 4
3. File-based approach Files Files Customer Applications File Applications Customer Customer Stock Orders File File Customer Order File Orders Stock Customer File File Customer Customer Stock Invoicing Invoicing File Order Order File File Purchase Stock File Orders Purchase Supplier Orders Supplier File File Stock Stock File Stock Control Control Order File Shared file approach 6
4. Outline ▪ File-based Approach ▪ Database Approach • Database Systems • Roles in the Database Environment • DBMSs ▪ Three-Schema Architecture and Data Independence ▪ Database Languages ▪ Data Models, Database Schema and Database State ▪ Data Management Systems Framework • Where are we? • Extending database capabilities for new applications ▪ Reading Suggestion: • [1,2]: Chapters 1, 2 8
5. Database Approach 10
6. Database Approach ▪ System catalog (metadata) provides description of data to enable program–data independence ▪ Logically related data comprises entities, attributes, and relationships of an organization’s information ▪ DataBase Management System (DBMS): a general-purpose software system that facilitates the processes of defining, constructing, manipulating, and sharing databases among various users and applications (or a software system that enables users to define, create, maintain, and control access to the database) 12
7. Database Approach ▪ Roles in the Database Environment • Database Administrator (DBA): responsible for authorizing access to DB, coordinating & monitoring its use, and for acquiring software and hardware resources as needed • Database Designers: responsible for identifying the data to be stored in DB, choosing appropriate structures to represent and store this data • Application Programmers • End Users • More details: see [1,2]-chapter 1
8. Database Approach ▪ Characteristics of the Database Approach • Self-describing nature of a database system • Insulation between programs and data, and data abstraction →Program-data independence + Program-operation independence = Data abstraction →A data model is a type of data abstraction • Support of multiple views of the data • Sharing of data and multi-user transaction processing • Other advantages of using the DBMS approach: see [1]-1.6 16
9. Example of Network Model Schema Slide 2- 18
10. Outline ▪ File-based Approach ▪ Database Approach • Database Systems • Roles in the Database Environment • DBMSs ▪ Three-Schema Architecture and Data Independence ▪ Database Languages ▪ Data Models, Database Schema and Database State ▪ Data Management Systems Framework • Where are we? • Extending database capabilities for new applications ▪ Reading Suggestion: • [1,2]: Chapters 1, 2 20
11. Three-Schema Architecture and Data Independence ▪ Three-level architecture and data independence 22
12. Three-Schema Architecture and Data Independence ▪ Internal Level • Physical representation of the database on the computer. • Describes how the data is stored in the database 24
13. Three-Schema Architecture and Data Independence ▪ Data Independence is the capacity to change the schema at one level of a database system without having to change the schema at the next higher level ▪ Logical Data Independence • Refers to immunity of external schemas to changes in conceptual schema • Conceptual schema changes (e.g. addition/removal of entities) should not require changes to external schema or rewrites of application programs 26
14. Three-Schema Architecture and Data Independence 28
15. Database Languages ▪ Data Definition Language (DDL) allows the DBA or user to describe and name entities, attributes, and relationships required for the application plus any associated integrity and security constraints ▪ Data Manipulation Language (DML) provides basic data manipulation operations on data held in the database ▪ Data Control Language (DCL) defines activities that are not in the categories of those for the DDL and DML, such as granting privileges to users, and defining when proposed changes to a databases should be irrevocably made 30
16. Outline ▪ File-based Approach ▪ Database Approach • Database Systems • Roles in the Database Environment • DBMSs ▪ Three-Schema Architecture and Data Independence ▪ Database Languages ▪ Data Models, Database Schema and Database State ▪ Data Management Systems Framework • Where are we? • Extending database capabilities for new applications ▪ Reading Suggestion: • [1,2]: Chapters 1, 2 32
17. Data Models, Database Schema and Database State ▪ Database Schema: the description of a database, which is specified during database design and is not expected to change frequently ▪ Schema Diagram: a displayed schema ▪ Database State (Snapshot): the data in the database at a particular moment in time 34
18. Data Management Systems Framework ▪ Where are we? Application Visualization, Collaborative Computing, Mobile Computing, Layer Knowledge-based Systems Layer 3: information extraction & sharing Data Warehousing, Data Mining, Internet DBs, Collaborative, P2P & Data Grid Data Management Management Layer 2: interoperability & migration Layer Heterogeneous DB Systems, Client/Server DBs, Multimedia DB Systems, Migrating Legacy DBs Layer 1: DB technologies DB Systems, Distributed DB Systems Supporting Networking, Mass Storage, Agents, Grid Computing Infrastructure, Parallel & Distributed Processing, Distributed Object Management Layer 36
19. Summary ▪ File-based Approach ▪ Database Approach ▪ Three-Schema Architecture and Data Independence ▪ Database Languages ▪ Data Models Database Schema and Database State ▪ Data Management Systems Framework (where are we?) ▪ Next week: ER Model 38