ics 541 - 01 (072)database systems background review 1 database systems background review dr....

ICS 541 - 01 (072) Database Systems Background Review

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Database Systems Background Review

Dr. Muhammad Shafique


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Outline

• Databases and Database Users• Database System Concepts and Architecture


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Databases and Database Users (1)

• Database concepts• Database

• A database represents some aspect of the real world

• A database is a logically coherent collection of data with some inherent meaning.

• A database is designed, built, and populated with data for a specific purpose.

• It has an intended group of users and some preconceived applications in which these users are interested.

• Database Management System• A database management system (DBMS) is a collection of

programs that enables users to create and maintain a database.


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• Typical DBMS Functionality• Define a database

• Construct or Load the Database

• Manipulating the database

• Concurrent Processing and Sharing

• Other features:• Protection or Security measures to prevent unauthorized access

• “Active” processing to take internal actions on data

• Presentation and Visualization of data


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• Characteristics of the Database Approach• Self-describing nature of a database system

• Insulation between programs and data• Data Abstraction

• program-data independence

• Support of multiple views of the data• Sharing of data and multi-user transaction processing


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• Database Users• Database administrators

• Database Designers

• End-users• Casual

• Naïve or Parametric

• Sophisticated

• Stand-alone


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• Advantages of Using the Database Approach• Controlling redundancy

• Sharing of data among multiple users

• Restricting unauthorized access to data

• Providing persistent storage

• Providing Storage Structures for efficient Query Processing

• Providing backup and recovery services

• Providing multiple interfaces to different classes of users

• Representing complex relationships among data

• Enforcing integrity constraints on the database

• Drawing Inferences and Actions using rules


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• Additional Implications of Using the Database Approach• Potential for enforcing standards

• Reduced application development time

• Flexibility to change data structures

• Availability of up-to-date information

• Economies of scale


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• Historical Development of Database Technology• Early Database Applications

• Hierarchical and Network Models

• Relational Model based Systems

• Object-oriented applications

• Data on the Web and E-commerce Applications


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• Extending Database Capabilities• Scientific Applications• Image Storage and Management• Audio and Video data management• Data Mining• Spatial data management• Time Series and Historical Data Management

The above gives rise to new research and development in incorporating new data types, complex data structures, new operations and storage and indexing schemes in database systems.


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Database System Concepts and Architecture (1)

• Data model• A collection of concepts that can be used to describe the

structure of a database

• Categories of data models• Conceptual (high-level, semantic) data models

• Logical/Implementation (representational) data models

• Physical (low-level, internal) data models


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• Schemas and Instances• Database Schema

• The description of a database is called the database schema, which is specified during database design and is expected not to change frequently

• Schema Diagram

• Schema Construct

• Database Instance• The actual data stored in a database at a particular moment in time.

Also called database state (or occurrence).


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• Database Schema Vs. Database State• Database State

• Initial Database State

• Valid State

• Distinction• The database schema changes very infrequently

• The database state changes every time the database is updated.

• Schema is also called intension, whereas state is called extension.


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• Three-Schema Architecture• Internal schema

• Conceptual schema

• External schemas

• Mappings • Transformations from one schema level to the other are

needed to translate requests and data.

• Programs refer to an external schema, and are mapped by the DBMS to the internal schema for execution


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• Data Independence• Logical Data Independence

• Physical Data Independence

• DBMS Languages• Data Definition Language (DDL)

• Storage Definition Language (SDL)

• View Definition Language (VDL)

• Data Manipulation Language (DML): • DML commands (data sublanguage) can be embedded in a

general-purpose programming language (host language)

• DML commands can be applied directly (query language).


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• DBMS Interfaces• Stand-alone query language interfaces• Programming interfaces

• Pre-compiler Approach• Procedure (Subroutine) Call Approach

• User-friendly interfaces• Menu-based• Forms-based• Graphics-based• Natural language

• Speech as Input (?) and Output• Web Browser• Parametric interfaces • Interfaces for the DBA


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• Database System Utilities• Loading data

• Backing up

• Reorganizing

• Performance monitoring

• Sorting

• User monitoring

• Data compression


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DBMS Component Modules


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Database System Architectures (1)

• Centralized


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• Client-Server (two-tier logical)


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• Client-Server (two-tier physical)


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• Client-Server (three-tier)• Presentation layer

• Business logic layer

• Database services layer


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References1. Textbook Chapter 12. Textbook Chapter 2


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Summary

• Databases and Database Users• Database System Concepts and Architecture

ics 541 - 01 (072)database systems background review 1 database systems background review dr....

Documents

database approachpotential

database systeminsulation

database construct

database approachself

database concurrent

real worlda database

datasharing of data

complex data structures