Download MANAGING DATA RESOURCES

FILE ORGANIZATION
• BIT: Binary Digit (0,1;Y,N;On, Off)
• BYTE: Combination of BITS which
represent a CHARACTER
• FIELD: Collection of BYTES which
represent a Fact
• RECORD: Collection of FIELDS
which reflect a TRANSACTION
• FILE: A Collection of Similar
RECORDS
Managing Digital Data
The layout of a personnel file in traditional file organization.
FILE ORGANIZATION
• DATABASE: An Organization’s Electronic
Library of FILES
• Primary FIELD or Key: Field in Each
Record Uniquely Identifies
THIS Record For
RETRIEVAL
UPDATING
SORTING
TRADITIONAL FILE ENVIRONMENT
(FLAT FILE)
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•
•
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DATA REDUNDANCY
PROGRAM / DATA DEPENDENCY
LACK OF FLEXIBILITY
POOR SECURITY
LACK OF DATA SHARING & AVAILABILITY
Different information making up a student record retained in three different sites.
DATABASE MANAGEMENT SYSTEM
(DBMS)
SOFTWARE TO CREATE & MAINTAIN DATA
*** ENABLES BUSINESS APPLICATIONS TO
EXTRACT DATA
*** INDEPENDENT OF SPECIFIC COMPUTER
PROGRAMS
DBMS
Managing Digital Data
• Traditional Files vs. Databases: Pros and
Cons
– Traditional File Advantages
• Simplicity
• Efficiency
• Customization
– Database Advantages
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•
•
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Reduced data redundancy
Application/data independence
Better control
Flexibility
COMPONENTS OF DBMS:
• THE SCHEMA: describe the structure of the
Database.
DATA DEFINITION LANGUAGE:
• Defines Data Elements in Database
• and Used to construct the schema
DATA MANIPULATION LANGUAGE:
• Manipulates Data for Applications
• DATA DICTIONARY:
– Maintains all information supplied by the
developer when constructing the schema
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DBMS
• Data Definition Language (DDL)
Data definition language to create a schema in NOMAD
Components of Database
Management Systems
• Data Manipulation Language (DML)
– Used to query the database
Figure 8.14 A Paradox query by example
DATA DICTIONARY
A typical data dictionary for a staff file
ADVANTAGES OF DBMS:
• REDUCES COMPLEXITY
• REDUCES DATA REDUNDANCY
• CENTRAL CONTROL OF DATA DEFINITIONS
• REDUCES PROGRAM / DATA DEPENDENCE
• REDUCES DEVELOPMENT / MAINTENANCE COSTS
• ENHANCES SYSTEM FLEXIBILITY
• INCREASES ACCESS / AVAILABILITY OF
INFORMATION
*
DBMS
Database Models
HIERARCHICAL DATA MODEL
– Records are related hierarchically –
each category is a subcategory of the next level up
– Disadvantages of hierarchical databases
• To retrieve a record, a user must start at the root and
navigate the hierarchy.
• If a link is broken, the entire branch is lost.
• Requires considerable data redundancy
ROOT
FIRST
CHILD
2nd
CHILD
Employer
Compensation
Ratings
Salary
Job
Assignments
Pension
Benefits
Insurance
Health
NETWORK DATA MODEL
• VARIATION OF HIERARCHICAL MODEL
• Allows a record to be linked to more than one
parent
• USEFUL FOR MANY-TO-MANY
RELATIONSHIPS
NETWORK
1
NETWORK
A
NETWORK
2
NETWORK
B
NETWORK
C
RELATIONAL DATA MODEL
• Consists of tables; links among entities are
maintained with foreign keys
• DATA IN TABLE FORMAT
– RELATION: TABLE
– TUPLE: ROW (RECORD) IN TABLE
– FIELD: COLUMN (ATTRIBUTE) IN TABLE
HOURS * RATE
ABLE
$ 40.50 $ 10.35
BAXTER $ 38.00 $ 8.75
CHEN
$ 42.70 $ 9.25
DENVER $ 35.90 $ 9.50
TOTAL
$ 419.18
$ 332.50
$ 394.98
$ 341.05
TYPES OR RELATIONS
ONE-TO-ONE:
STUDENT
CLASS
ONE-TO-MANY:
STUDENT
A
MANY-TO-MANY:
ID
STUDENT
B
CLASS
1
STUDENT
C
CLASS
2
STUDENT STUDENT
A
B
STUDENT
C
Relational Operations
• Data Manipulation
– Select : is the selection of records that meets certain condition.
– Project: is the selection of certain columns from a table.
– Join
: is the joining of data from multiple tables.
• Structured Query Language (SQL)
– International standard DDL and DML for
relational DBMS.
– Advantages of using SQL
Users do not need to learn different DDLs and DMLs.
SQL can be embedded in widely used 3rd generation
languages, increasing efficiency and effectiveness.
Programmer not forced to rewrite statements since SQL
statements are portable.
Database Models
Advantages and disadvantages of database models
Database Architecture
• Shared Resource and Client/Server
Systems
– Four basic client/server models
• Applications run at a server
• Applications run on local PCs
• Applications run on both the local PCs and the
server
• Applications and key elements of the database
are split between the PCs and the server
Database Architecture
• Distributed Databases
– Replication :Full copy of the entire database is
stored at all sites
A replicated database: each computer holds a copy of the entire database
Database Architecture
– Fragmentation: Parts of database are stored where they
are most often accessed
A fragmented database: each computer holds only the part of the database that is most
frequently accessed by the local users
Web Databases
• Databases on the Web
–
–
–
–
Catalogs
Libraries
Directories
Client lists and profiles
• When linking a database to the Internet,
consider
• Which application to use
• How to ensure Web surfers do not interfere with database
updates
• How to maintain security
Data Warehousing
• Data warehouse
– Collection of data that supports management
decision making
– Phases in Building a Data Warehouse
• Extraction Phase
• Cleansing Phase
• Loading Phase
• Data Mining
– Selecting, exploring, and modeling data to discover
unknown relationships
OPERATIONAL,
HISTORICAL DATA
Data
Warehousing
INTERNAL
DATA
SOURCES
DATA WAREHOUSE
DATA
ACCESS &
ANALYSIS
EXTRACT,
TRANSFORM
INFORMATION
DIRECTORY
EXTERNAL
DATA
SOURCES
QUERIES &
REPORTS
OLAP
DATA MINING
Data-Mining
Potential applications of data-mining
DATABASE ADMINISTRATION
• DEFINES & ORGANIZES DATABASE
STRUCTURE AND CONTENT
• DEVELOPS SECURITY PROCEDURES
• DEVELOPS DATABASE DOCUMENTATION
• MAINTAINS DBMS
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Ethical and Societal Issues
A Too-Risky Info Highway
• Out of Hand -- Out of Control
– DBMSs allow organizations to collect, maintain,
and sell vast amounts of private personal data
easily.
• Where is the Information Going?
– Many consumers provide information daily without
being aware of where it is actually going.
– http://www.publicrecordfinder.com/
• The Upside
– Database technology enables better and faster
services.