The Context of Database Management

1
The Context of Database Management

• Chapter 1, McFadden, Hoffer Prescott

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
• 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
FILE SYSTEM
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
ACCESS ENGINE
METADATA
DATA
9
What is a Database Management System?

• Data Files contain the values that are stored
• Directory contains the meta-data
• Access Engine does the work of locating and
  displaying specific data values
• Utility Programs perform support functions such
  as backup of accounting

10
Example of Data
11
Example of Metadata
12
Files and Databases

• Metadata
• Data about data
• Description of fields
• Display and format instructions
• Structure of files and tables
• Security and access rules
• Triggers and operational rules

13
Database Access
USER INTERFACE
DATABASE
PROGRAM
14
Evolution of data Structures
15
History of Database Management

• File Management Systems
• Hierarchical Model
• IBM Information Management System (IMS) 1966
• Network Model
• Charles Bachmans Integraded Data Store (IDS)
  1965
• Conference on Data Systems Languages /DataBase
  Task Group CODASYL/DBTG (1971)
• Relational Model
• E.F. Codd, 1970

16
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.

17
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.
18
Network
SECTION
STUDENT
INSTRUCTOR
COLLEGE
Each file can have several parents. Both SECTION
and COLLEGE are parent files..
19
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.

20
Relational
SECTION
SECTION-STUDENT SECTION-KEY STUDENT-KEY
SECTION-INSTRUCTOR SECTION-KEY INSTRUCTOR-KEY
INSTRUCTOR COLLEGE-KEY
COLLEGE
Each file can have several parents. Both SECTION
and COLLEGE are parent files..
21
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.

22
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)

23
(No Transcript)
24
(No Transcript)