1 1 File Systems and Databases Chapter 1 The Worlds of Database Systems Prof. Sin-Min Lee Dept. of Computer Science

1 1 Tuesday Thursday 10:15 – 11:30

1 1 ??! Your evaluation in this course is determined by: 30% Class Presentation 10% Presentation report 5%

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1 1 u The mediocre teacher tells. u The good teacher explains. u The superior teacher demonstrates. u The great teacher inspires.

1 1 Files and Databases 4File: A collection of records or documents dealing with one organization, person, area or subject (Rowley) u Manual (paper) files u Computer files 4Database: A collection of similar records with relationships between the records (Rowley) u Bibliographic, statistical, business data, images, etc.

1 1 Introducing the Database 4Major Database Concepts u Data and information l Data - Raw facts l Information - Processed data u Data management u Database u Metadata u Database management system (DBMS)

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1 1 Figure 1.1 Sales per Employee for Each of ROBCOR’S Two Divisions

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1 1 Database Systems 4Types of Database Systems u Number of Users l Single-user –Desktop database l Multiuser –Workgroup database –Enterprise database u Scope l Desktop l Workgroup l Enterprise

1 1 Database Systems 4Types of Database Systems u Location l Centralized l Distributed u Use l Transactional (Production) l Decision support l Data warehouse

1 1 Database 4A Database is a collection of stored operational data used by the application systems of some particular enterprise (C.J. Date) u Paper “Databases” l Still contain a large portion of the world’s knowledge u File-Based Data Processing Systems l Early batch processing of (primarily) business data u Database Management Systems (DBMS)

1 1 Why DBMS? 4History u 50’s and 60’s all applications were custom built for particular needs u File based u Many similar/duplicative applications dealing with collections of business data u Early DBMS were extensions of programming languages u E.F. Codd and the Relational Model u Ashton-Tate and first Microcomputer DBMS

1 1 File Based Systems Naughty Nice Just what asked for Coal Estimation Delivery List Application File Toys Addresses Toys

1 1 From File Systems to DBMS 4Problems with file processing systems u Inconsistent data u Inflexibility u Limited data sharing u Poor enforcement of standards u Excessive program maintenance

1 1 DBMS Benefits 4Minimal data redundancy 4Consistency of data 4Integration of data 4Sharing of data 4Ease of application development 4Uniform security, privacy, and integrity controls 4Data accessibility and responsiveness 4Data independence 4Reduced program maintenance

1 1 Terms and Concepts 4Data independence u Physical representation and location of data and the use of that data are separated l The application doesn’t need to know how or where the database has stored the data, but just how to ask for it l Moving a database from one DBMS to another should not have a material effect on application program l Recoding, adding fields, etc. in the database should not affect applications

1 1 Database Environment CASE Tools DBMS User Interface Application Programs Repository Database

1 1 Database Components DBMS =============== Design tools Table Creation Form Creation Query Creation Report Creation Procedural language compiler (4GL) ============= Run time Form processor Query processor Report Writer Language Run time User Interface Applications Application Programs Database Database contains: User’s Data Metadata Indexes Application Metadata

1 1 Types of Database Systems 4PC databases 4Centralized database 4Client/server databases 4Distributed databases 4Database models

1 1 PC Databases E.g.: Access FoxPro Dbase Etc.

1 1 Centralized Databases Central Computer

1 1 Client Server Databases Network Client Database Server

1 1 Distributed Databases computer Location A Location C Location B Homogeneous Databases

1 1 Distributed Databases Local Network Database Server Client Comm Server Remote Comp. Remote Comp. Heterogeneous Or Federated Databases

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1 1 Introducing the Database 4Importance of DBMS u It helps make data management more efficient and effective. u Its query language allows quick answers to ad hoc queries. u It provides end users better access to more and better-managed data. u It promotes an integrated view of organization’s operations -- “big picture.” u It reduces the probability of inconsistent data.

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1 1 Figure 1.2 The DBMS Manages the Interaction Between the End User and the Database

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1 1 Introducing the Database 4Why Database Design Is Important? u A well-designed database facilitates data management and becomes a valuable information generator. u A poorly designed database is a breeding ground for uncontrolled data redundancies. u A poorly designed database generates errors that lead to bad decisions.

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1 1 Historical Roots 4Why Study File Systems? u It provides historical perspective. u It teaches lessons to avoid pitfalls of data management. u Its simple characteristics facilitate understanding of the design complexity of a database. u It provides useful knowledge for converting a file system to a database system.

1 1 Figure 1.3 Contents of the CUSTOMER File

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1 1 Table 1.1 Basic File Terminology

1 1 Figure 1.4 Contents of the AGENT File

1 1 A Simple File System Figure 1.5

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1 1 File System Critique 4File System Data Management u File systems require extensive programming in a third-generation language (3GL). u As the number of files expands, system administration becomes difficult. u Making changes in existing file structures is important and difficult. u Security features to safeguard data are difficult to program and usually omitted. u Difficulty to pool data creates islands of information.

1 1 File System Critique 4Structural and Data Dependence u Structural Dependence A change in any file’s structure requires the modification of all programs using that file. u Data Dependence A change in any file’s data characteristics requires changes in all data access programs. u Significance of data dependence is the difference between the data logical format and the data physical format. u Data dependence makes file systems extremely cumbersome from a programming and data management point of view.

1 1 File System Critique 4Field Definitions and Naming Conventions u A good (flexible) record definition anticipates reporting requirements by breaking up fields into their components. l Example: –Customer Name  Last Name, First Name, Initial –Customer Address  Street Address, City, State

1 1 File System Critique 4Field Definitions and Naming Conventions u Selecting proper field names is very important. l Names must be as descriptive as possible within restrictions. l Naming must reflect designer’s documentation needs and user’s reporting and processing requirements.

1 1 File System Critique 4Data Redundancy: Uncontrolled data redundancy sets the stage for u Data Inconsistency (lack of data integrity) u Data anomalies l Modification anomalies l Insertion anomalies l Deletion anomalies

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1 1 Figure 1.7 The Database System Environment Figure 1.7

1 1 Database Systems 4The Database System Components u Hardware l Computer l Peripherals u Software l Operating systems software l DBMS software l Applications programs and utilities software

1 1 Database Systems 4The Database System Components u People l Systems administrators l Database administrators (DBAs) l Database designers l Systems analysts and programmers l End users u Procedures l Instructions and rules that govern the design and use of the database system u Data l Collection of facts stored in the database

1 1 Database Systems 4The Database System Components u The complexity of database systems depends on various organizational factors: l Organization’s size l Organization’s function l Organization’s corporate culture l Organizational activities and environment u Database solutions must be cost effective AND strategically effective.

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1 1 Conceptual Design includes Operational Use Mini World Requirements collection & analysis Conceptual design Data model design Physical design Database requirements Conceptual schema (in a high level data model) Conceptual schema (in the data model of a specific DBMS Internal schema (for the same DBMS) DBMS Independent DBMS specific Data Definition Language Statements Processing Requirements Transaction Design DBMS independent Transaction Implementation