1 CSBP430 – Database Systems Chapter 1: Databases and Database Users Mamoun Awad College of Information Technology United Arab Emirates University

2 In this chapter, you will learn: Basic Definitions Example of a Database Main Characteristics of Database Technology Additional Benefits of Database Technology When Not to Use a DBMS

3 Basic Definitions Database: A collection of related data. Data: Known facts that can be recorded and have an implicit meaning. Mini-world: Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university. Database Management System (DBMS): A software package/system to facilitate the creation and maintenance of a computerized database. Database System: The DBMS software together with the data itself. Sometimes, the applications are also included.

4 File Terminology Data: Raw Facts Field: Group of characters with specific meaning Record: Logically connected fields that describe a person, place, or thing File: Collection of related records

5 Simple File System

6 File System Critique File System Data Management Requires extensive programming in third- generation language (3GL) Time consuming Makes ad hoc queries impossible Leads to islands of information

7 File System Critique (con’t.) Data Dependence Change in file’s data characteristics requires modification of data access programs Must tell program what to do and how Makes file systems cumbersome from programming and data management views Structural Dependence Change in file structure requires modification of related programs

8 File System Critique (con’t.) Data Redundancy Different and conflicting versions of same data Results of uncontrolled data redundancy Data anomalies –Modification –Insertion –Deletion Data inconsistency –Lack of data integrity

9 Database Systems Database consists of logically related data stored in a single repository Provides advantages over file system management approach Eliminates inconsistency, data anomalies, data dependency, and structural dependency problems Stores data structures, relationships, and access paths

10 Database vs. File Systems

11 Database System Environment

12 Example of a Database (with a Conceptual Data Model) Mini-world for the example: Part of a UNIVERSITY environment. Some mini-world entities: - STUDENTs - COURSEs - SECTIONs (of COURSEs) - (academic) DEPARTMENTs - INSTRUCTORs Some mini-world relationships: - SECTIONs are of specific COURSEs - STUDENTs take SECTIONs - COURSEs have prerequisite COURSEs - INSTRUCTORs teach SECTIONs - COURSEs are offered by DEPARTMENTs - STUDENTs major in DEPARTMENTs

13

14

15 Main Characteristics of Database Technology Self-contained nature of a database system: A DBMS catalog stores the description of the database. The description is called meta-data). This allows the DBMS software to work with different databases. Insulation between programs and data: Called program-data independence. Allows changing data storage structures and operations without having to change the DBMS access programs. Data Abstraction: A data model is used to hide storage details and present the users with a conceptual view of the database. Support of multiple views of the data: Each user may see a different view of the database, which describes only the data of interest to that user.

16

17 Additional Benefits of Database Technology Controlling redundancy in data storage and in development and maintenance efforts. Sharing of data among multiple users. Restricting unauthorized access to data. Providing multiple interfaces to different classes of users. Representing complex relationships among data. Enforcing integrity constraints on the database. Providing backup and recovery services. Potential for enforcing standards. Flexibility to change data structures. Reduced application development time. Availability of up-to-date information. Economies of scale.

18

19 Importance of DBMS Makes data management more efficient and effective Query language allows quick answers to ad hoc queries Provides better access to more and better-managed data Promotes integrated view of organization’s operations Reduces the probability of inconsistent data

20 DBMS Manages Interaction

21 Database Design Importance of Good Design Poor design results in unwanted data redundancy Poor design generates errors leading to bad decisions Practical Approach Focus on principles and concepts of database design Importance of logical design

22 Database Models and the Internet Characteristics of “Internet age” databases Flexible, efficient, and secure Internet access Easily used, developed, and supported Supports complex data types and relationships Seamless interfaces with multiple data sources and structures Simplicity of conceptual database model Many database design, implementation, and application development tools Powerful DBMS GUI make DBA job easier

23 When not to use a DBMS Main inhibitors (costs) of using a DBMS: High initial investment and possible need for additional hardware. Overhead for providing generality, security, recovery, integrity, and concurrency control. 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. 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.