Data Modeling

Download Report

Transcript Data Modeling

MANAGING
INFORMATION
TECHNOLOGY
FIFTH EDITION
CHAPTER 5
THE DATA RESOURCE
E. Wainright Martin  Carol V. Brown  Daniel W. DeHayes
Jeffrey A. Hoffer  William C. Perkins
WHY MANAGE DATA?
 Organizations could not function long
without critical business data
 Cost to replace data would be very high
 Time to reconcile inconsistent data may
be too long
 Data often needs to be accessed quickly
© 2005 Pearson Prentice-Hall
Chapter 5 - 2
Page 135
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Data model –
overall map for business data needed to effectively
manage the data
 Data modeling involves:
Methodology, or steps followed to identify
and describe data entities
 Notation, or a way to illustrate data entities
graphically

© 2005 Pearson Prentice-Hall
Chapter 5 - 3
Page 135
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
The Data Model
 Entity-relationship diagram (ERD)
Most common method for representing a
data model and organizational data needs
 Captures entities and their relationships

Entities – things about which data are
collected
 Attributes – actual elements of data that are
to be collected

© 2005 Pearson Prentice-Hall
Chapter 5 - 4
Page 135
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
The Data Model
NOTE:
• Entities are Customer, Order, and Product.
• Attributes of the Customer entity could be
customer last name, first name, street, city, …
© 2005 Pearson Prentice-Hall
Chapter 5 - 5
Figure 5.1 Entity-Relationship Diagram
Page 135
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Data Modeling
 Enterprise modeling (a process focus)
Top-down approach
Describes organization and data
requirements at high level, independent of
reports, screens, or detailed specifications
 Not biased by how business operates today


© 2005 Pearson Prentice-Hall
Chapter 5 - 6
Page 136
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Data Modeling
Enterprise Modeling Steps:

Divide work into major
functions

Divide each function into
processes

Divide processes into
activities

List data entities
assigned to each activity

Identify relationships
between entities
© 2005 Pearson Prentice-Hall
Chapter 5 - 7
Figure 5.2 Enterprise Decomposition
for Data Modeling
Page 136
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Data Modeling
 View integration (a data output focus)


Bottom-up approach
Each report, screen, form, document
produced from databases first … each
called a user view
© 2005 Pearson Prentice-Hall
Chapter 5 - 8
Page 136
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Data Modeling
View Integration Steps:
 Create user views
 Identify data elements in each user view and put into a
structure called a normal form
 Normalize user views
 Integrate set of entities from normalization into one
description
Normalization –
process of creating simple data structures from more complex
ones
© 2005 Pearson Prentice-Hall
Chapter 5 - 9
Page 136
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Database Architecture
Database –
shared collection of logically related data, organized to
meet needs of an organization
Database Architecture –
way in which the data are structured and stored in the
database
© 2005 Pearson Prentice-Hall
Chapter 5 - 10
Page 137
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Database Architecture
 Six basic database architectures:
1.
2.
3.
4.
Hierarchical (top-down organization)
Network (high-volume transaction processing)
Relational (data arranged in simple tables)
Object-oriented (data and methods encapsulated in object
classes)
5.
6.
Object-relational (hybrid of relational and objectoriented)
Multidimensional (used by data warehouses)
© 2005 Pearson Prentice-Hall
Chapter 5 - 11
Page 138
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Tools for Managing Data
 A DBMS helps manage data by providing
seven functions:
Data storage, retrieval, update
2. Backup
3. Recovery
4. Integrity control
5. Security control
6. Concurrency control
7. Transaction control
1.
© 2005 Pearson Prentice-Hall
Chapter 5 - 12
Page 139
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Tools for Managing Data
Data Dictionary/Directory (DD/D) –
central encyclopedia of data definitions and usage
information … a database about data
 Contains:
 Definition of each entity,
relationship, and data
element
 Display formats
 Integrity rules
© 2005 Pearson Prentice-Hall
Chapter 5 - 13



Security restrictions
Volume and sizes
List of applications that use
the data
Page 139-140
TECHNICAL ASPECTS OF
MANAGING THE DATA RESOURCE
Database Programming
Query language –
a 4 GL, nonprocedural programming language to obtain
data from a database, often provided by the DBMS
SQL query language example:
SELECT ORDER#, CUSTOMER#, CUSTNAME,
ORDER-DATE FROM CUSTOMER, ORDER
WHERE ORDER-DATE > ’04/12/05’
AND CUSTOMER.CUSTOMER# =
ORDER.CUSTOMER#
© 2005 Pearson Prentice-Hall
Chapter 5 - 14
Page 140
MANAGERIAL ISSUES IN
MANAGING DATA
Principles in Managing Data



The need to manage data is permanent
Data can exist at several levels
Application software should be separate from the
database
 Application software can be classified by how they
treat data
1. Data capture
2. Data transfer
3. Data analysis and presentation
© 2005 Pearson Prentice-Hall
Chapter 5 - 15
Page 140
© 2005 Pearson Prentice-Hall
Chapter 5 - 16
Figure 5.4
Page 142
MANAGERIAL ISSUES IN
MANAGING DATA
The Data Management Process
© 2005 Pearson Prentice-Hall
Chapter 5 - 17
Figure 5.6 Asset Management Functions
Page 144
MANAGERIAL ISSUES IN
MANAGING DATA
Data Administration
Key functions of the data administration group:

Promote and control data sharing

Analyze the impact of changes to application systems when data
definitions change

Maintain the data dictionary

Reduce redundant data and processing

Reduce system maintenance costs and improve system
development productivity

Improve quality and security of data

Insure data integrity
© 2005 Pearson Prentice-Hall
Chapter 5 - 18
Page 150
MANAGERIAL ISSUES IN
MANAGING DATA
Data Administration
Key functions of the database administrator (DBA):

Tuning database management systems.

Selection and evaluation of and training on database technology.

Physical database design.

Design of methods to recover from damage to databases.

Physical placement of databases on specific computers and
storage devices.

The interface of databases with telecommunications and other
technologies.
© 2005 Pearson Prentice-Hall
Chapter 5 - 19
Page 150-151