1. The Context of Database Management
Chapter 1, McFadden, Hoffer & Prescott
Delivered 8/20/98

2. Data and Information
DATA: Facts concerning people, objects, vents or other entities. Databases store data.
INFORMATION: Data presented in a form suitable for interpretation.
Data is converted into information by programs and queries. Data may be stored in files or in databases. Neither one stores information.
KNOWLEDGE: Insights into appropriate actions based on interpreted data.

3. Knowledge Generation
DATA
INFORMATION

4. Basic Principles
DATABASE: A shared collection of interrelated data designed to meet the varied information needs of an organization.
DATABASE MANAGEMENT SYSTEM: A collection of programs to create and maintain a database.
Define
Construct
Manipulate

5. Files or Databases Files Databases program-data dependence
duplication of data
limited data sharing
lengthy development time
excessive program maintenance
a lot of experienced programmers and developers
robust technology
Databases
program-data independence
minimal data redundancy
improved data consistency, quality, accessibility, and sharing
increased productivity and less maintenance

6. Database vs File Systems
Program 1
Meta-Data
Data
Program 2
Meta-Data
Program 3
Meta-Data
DATABASE
Program 1
Meta-
Data
Data
Program 2
Program 3

7. Objectives of a DBMS Approach
SELF-DESCRIBING
DATA INDEPENDENCE
MULTIPLE VIEWS
MULTIPLE USERS

8. Database Management Systems
UTILITY
PROGRAMS
DATA
ACCESS ENGINE
METADATA

9. Example of Data

10. Example of Metadata

11. Database Access
USER
INTERFACE
DATABASE
PROGRAM

12. Evolution of data Structures

13. History of Database Management
File Management Systems
Hierarchical Model
IBM “Information Management System (IMS)” 1966
Network Model
Charles Bachman’s “Integraded Data Store (IDS)” 1965
Conference on Data Systems Languages /DataBase Task Group CODASYL/DBTG (1971)
Relational Model
E.F. Codd, 1970

14. File Management Systems
Provided facilities to extract data and share files, but did not implement any way to connect records in one file to those in another. Relationships had to be implemented in application code.

15. Hierarchy SECTION STUDENT INSTRUCTOR COLLEGE COLLEGE
Each file can have only one parent. To implement a second “parent” (COLLEGE) we have to implement a shadow copy.

16. Network SECTION STUDENT INSTRUCTOR COLLEGE
Each file can have several parents. Both SECTION and COLLEGE are “parent” files..

17. Structured Databases
Relationships were implemented by physical pointers (called “sets”) which allowed records to be connected in different files. Hierarchical databases allow only one parent set; networks allow several. These permit efficient processing but the sets must be constructed on data entry and cannot be rearranged later.

18. Relational SECTION SECTION-STUDENT SECTION-INSTRUCTOR STUDENT
SECTION-KEY
STUDENT-KEY
SECTION-INSTRUCTOR
SECTION-KEY
INSTRUCTOR-KEY
STUDENT
COLLEGE-KEY
INSTRUCTOR
COLLEGE-KEY
COLLEGE
Each file can have several parents. Both SECTION and COLLEGE are “parent” files..

19. Relational Models
Relational models implement relationships with matched data values in related files (called primary and foreign keys). Any attributes can be matched. The connection is established at retrieval so interconnections can be developed as needed.

20. Relational Terminology
Entity
Person, place, thing or event about which we wish to keep data
Attribute
property of an entity
Relationship
an association among entities (entity records)