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

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.

Knowledge Generation DATA INFORMATION

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

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

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

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

Database Management Systems UTILITY PROGRAMS DATA ACCESS ENGINE METADATA

Example of Data

Example of Metadata

Database Access USER INTERFACE DATABASE PROGRAM

Evolution of data Structures

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

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.

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.

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

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.

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..

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.

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)