1. Chapter 2: Database System Concepts and Architecture
Presentation slides for
DATABASE SYSTEMS by
Muhammad Waheed Aslam
KFUPM
Information & Computer Science Department

2. Outline Data Models, Schemas, and Instances
Categories of Data Models
Schemas, Instances, and Database State
DBMS Architecture and Data Independence
The Three-Schema Architecture
Data Independence
Database Languages and Interfaces
DBMS Languages
DBMS Interfaces

3. Outline The Database System Environment
DBMS Component Modules
Database System Utilities
Tools, Application Environments, and Communications Facilities
Classification of Database Management Systems

4. Data Models, Schemas, and Instances
A collection of concepts that can be used to describe the structure of a database
By the structure we mean the data types, relationships, and constraints that should hold on the data
Also includes basic operations for specifying retrievals and updates on the database
It is becoming more common to include concepts to specify the dynamic aspect or behavior of a database application

5. Categories of Data Models
Conceptual (high-level)
Provide concepts that are close to the way many users perceive data (Also called entity-based, object-based data models)
Physical (low-level)
Provide concepts that describe details of how data is stored in the computer
Meant for computer specialists, not for typical end users
Implementation (representational)
Provide concepts that may be understood by end users but that are not too far removed from the way data is organized within the computer
Hide some details of data storage but can be implemented on a computer system in a direct way

6. Schemas, Instances, and DB State
Database Schema (intension)
The description of a database
Not expected to change frequently
Schema Diagram
A diagrammatic display of (some aspects of) a database schema.
Database State (extension)
The data in the database at a particular moment of time
Also called the current set of occurrences or instances
Every update operation changes the database from one state to another

7. The Three-Schema Architecture
Internal Schema
Describes the physical storage structure
Uses a physical data model
Conceptual Schema
Describes the structure of the whole database
Uses a conceptual or an implementation data model
External Schema
Includes a number user views
Mappings
The process of transforming requests and results between levels

8. The Three-Schema Architecture

9. Data Independence Logical Data Independence Physical Data Independence
The capacity to change the conceptual schema without having to change the external schema or application programs
Physical Data Independence
The capacity to change the internal schema without having to change the conceptual schema
Advantages and disadvantages
The three -Schema Architecture can make it easier to achieve true data independence
Mappings create an overhead during compilation or execution of a query or a program
Not implemented fully by DBMSs

10. DBMS Languages Data Definition Language (DDL)
Used by the DBA and database designers to define the conceptual schema of a a database
In many DBMSs, the DDL is also used to define the internal and external schemas
In some DBMSs, separate storage definition (SDL) and view definition language (VDL) are used to define internal and external schemas
Data Manipulation Language (DML)
DML commands can be used as stand-alone (query language) or can be embedded within a general-purpose language
Procedural DML - allows user to tell system exactly how to manipulate data
Non-Procedural DML - allows user to state what data is needed rather than how it is to be retrieved

11. DBMS Interfaces Menu-based Interfaces for Browsing
Forms-based Interfaces
Graphical User Interfaces
Natural Language Interfaces
Interfaces for Parametric Users
Interfaces for The DBA

12. DBMS Component Modules

13. Database System Utilities
Loading
Backup
File Reorganization
Performance monitoring
Other Utilities
Sorting files
Handling data compression
Monitoring access by users

14. Tools, Application Environments, and Communications Facilities
CASE tools
Used in the design phase
Expanded Data Dictionary(information repository)
Stores catalog information about schemas and constraints
Stores other information such as design decisions, usage standards, application program descriptions, and user information
Application Development Environments
Provide an environment for developing database applications
Include facilities for database design, GUI development, querying and updating, and application program development
Communications software
Allow users to access database from remote location

15. Classification of DBMSs
Data Model
Number of Users
Number of Sites
Cost
Types of Access Path
Purpose