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Mgt 20600:
IT Management & Applications
Networks (cont.)
Databases
Thursday
October 13, 2005
Reminders




Reading
– For today
 Fundamentals text, Chapter Three, Organizing Data and Information chapter
– For the Thursday after break
 Fundamentals text, Chapter 6, Information and Decision Support Systems
Homework
– Database/DSS homework will be posted tomorrow
– Due October 28th: Friday after fall break
Exams
– Medians of 58.6 (Section 3) and 59.5 (Section 4)
 Nice work for many of you!
 If you didn’t do as well as you like, still many hundreds of points to go in the
course
 Suggestions
– Always do reading ahead of time, not just before exam
– Always come to class
– Take the homeworks seriously and review them before the exams
– Come and see me and Christine for help with exam review
Next week: Fall break!
Telecommunications and
Networks
Elements of a Telecommunications System
Transmission Media
Wired Transmission Media Types
Wired Media Types
Wireless Transmission
Media Types

Radio Waves
– Bluetooth



Short distances only
Relatively slow transmission speed
Developed for inter-device communications
– Wi-Fi



Standard supports up to 54Mbps
Supports longer distances than bluetooth
Infrared
– Signals sent as light waves
– Short distance
– Unobstructed line of sight

Microwave
–
–
–
–

High frequency radio signal
Capable of high-speed transmission
Unobstructed line of sight
Susceptible to interference
Cellular
Networks
 Computer
network: the
communications media, devices, and
software needed to connect two or
more computer systems or devices
 Network nodes: the computers and
devices on the networks
Network Types
 Personal
area network (PAN)
 Local area network (LAN)
 Metropolitan area network (MAN)
 Wide area network (WAN)
 International network
Network Types
A Typical LAN
Network Types
Is the internet
a wide area
network?
A Wide Area Network
Communications Software and
Protocols

Communications software: software
that provides a number of important
functions in a network, such as error
checking and data security
– Network operating system (NOS)
– Network management software
– Communications protocol: a standard set of
rules that controls a telecommunications
connection
 Example,
TCP/IP protocol that underlies the Internet
The Internet
 Internet:
a collection of
interconnected networks, all freely
exchanging information
 ARPANET
– The ancestor of the Internet
– A project started by the U.S.
Department of Defense (DoD) in 1969
How the Internet Works

Data is passed in chunks called packets
– Internet Protocol (IP)
 Communications
standard that enables traffic to be
routed from one network to another as needed
 Every computer attached to internet has an IP
address
– Transmission Control Protocol (TCP)
 Widely
used transport-layer protocol that is used in
combination with IP by most Internet applications
 In charge of communication session between two
computers
– Uniform Resource Locator (URL)
 Assigned
addresses for web servers and the web
pages they provide
How the Internet Works
Routing Messages over the Internet
Accessing the Internet
Several Ways to Access the Internet
Internet Service Providers
 Internet
service provider (ISP):
any company that provides
individuals or organizations with
access to the Internet
– Most charge a monthly fee
– Many ISPs and online services offer
broadband Internet access through
digital subscriber lines (DSLs), cable, or
satellite transmission
Applications that run over the
Internet
World Wide Web
 Instant Messaging
 Email
 File Transfer Protocol
 Telnet
 All of these are

– Software applications
– Designed for the internet
– All assume your computer understands TCP/IP
The World Wide Web
 Hypertext
Transfer Protocol
(HTTP): Protocol that web servers
and browsers use to send requests
and information
 Hypertext Markup Language
(HTML): the standard page
description language for Web pages
Intranets and Extranets
 Intranet
– Internal corporate network built using
Internet and World Wide Web standards
and products
– Used by employees to gain access to
corporate information
– Slashes the need for paper
Intranets and Extranets
 Extranet
– A network based on Web technologies
that links selected resources of a
company’s intranet with its customers,
suppliers, or other business partners
 Virtual
private network (VPN)
– Secure connection between two points
across the Internet
– Intranets and extranets often run over
VPN’s
Internet Issues
 Privacy
– Spyware: hidden files and information
trackers that install themselves secretly
when you visit some Internet sites
– Cookie: a text file that an Internet
company can place on the hard disk of a
computer system
Net Issues

Security
– Cryptography: converting a message into a
secret code and changing the encoded
message back to regular text
– Digital signature: encryption technique used
to verify the identity of a message sender for
processing online financial transactions
– Firewall: a device that sits between an
internal network and the Internet, limiting
access into and out of a network based on
access policies
Net Issues
Databases
A well-designed and well-managed
database is an extremely valuable tool in
supporting decision making
 Databases are key corporate assets
 Databases are the foundation for
sophisticated analyses that provide
business intelligence

– What new products to design
– How to market to particular customer groups
– Which customer groups are the most profitable
Traditional Approach
to Data Management
Traditional
approach: separate
data files are
created for each
application
Results in data
redundancy
(duplication)
Data
redundancy
conflicts with
data integrity
Database Approach
to Data Management
Database approach:
pool of related data is
shared by multiple
applications
Significant
advantages over
traditional
approach
Advantages of Database Approach
Improved strategic use of data
 Reduced data redundancy
 Improved data integrity
 Easier modification and updating
 Data and program independence
 Better access to data and information
 Standardization of data access
 A framework for program development
 Better overall protection of the data
 Shared data and information resources

Disadvantages of the
Database Approach
 More
complexity
 More difficult to recover from a
failure
 More expensive
Databases
 Databases
must contain
– Accurate information
– Right kinds of information
– Current information
– Information from all organizational
functions
Database Data

Data regarding
– Important entities
 Customers
 Suppliers
 Transactions
– Each entity will have a number of attributes
about which you want to collect and store
information
 Customer
address
 Customer phone number
 Customer account number
Entities, Attributes, Keys
Entity: a generalized class of people,
places, or things (objects) for which
data is collected, stored, and
maintained (Table and records)
Attribute: a characteristic of an
entity (fields)
Data item: a value of an attribute
(fields)
Key: field(s) that identify a record
Primary key: field(s) that uniquely
identify a record
Hierarchy of Data
Field: name, number, or
characters that describe
an aspect of a business
object or activity
Record: a collection of
related data fields
File: a collection of
related records
Database: a collection of
integrated and related
files
Data Modeling and the
Relational Database Model
 When
building a database, consider:
– Content: What data should be collected,
at what cost?
– Access: What data should be provided
to which users, and when?
– Logical structure: How should data be
arranged to make sense to a given
user?
– Physical organization: Where should
data be physically located?
Data Modeling
 Building
a database requires two
types of design
– Logical design
 Shows
an abstract model of how data
should be structured and arranged to meet
an organization’s information needs
– Physical design
 Fine-tunes
the logical database design for
performance and cost considerations
Data Modeling
 Data
model: a diagram of data
entities and their relationships
 Entity-relationship (ER)
diagrams: data models that use
basic graphical symbols to show the
organization of and relationships
between data
Data Modeling
An Entity-Relationship (ER) Diagram for a
Customer Order Database
The Relational Database Model
Relational model: all data elements are
placed in two-dimensional tables
(relations), which are the logical
equivalent of files
 In the relational model:

– Each table represents a data entity
– Each row of a table represents a specific
instance of a data entity
– Columns of the table represent attributes
The Relational Database Model
A Relational Database Model