Chapter 4
Information and Databases
Chapter Outline
 Data Modeling: Documenting Information
Architecture
 User’s View of a Computerized Database
 Database Management Systems
 Text Databases and Hypertext
 Evaluating Information Used in Business
Processes
 Models as Components of Information Systems
Data Modeling: Documenting
Information Architecture
 Entity-Relationship Diagrams
 Identifying the Data in Information Systems
An information architecture
 What information is in a system?
 How is the information organized?
 How can users get the information they
want?
 Are these points independent?
 How can we represent this? Do we need a
tool?
A model for representing
information and relationships
 What kinds of things are important in this
system?
 How are these things (entities) related?
 What information (attributes) are collected
about these things?
Entity Relationship Diagram
So…what do these symbols
mean?
Symbols in an ERD
Attributes (information) about
our entities (from Alter pp. 113)
PROFESSOR
DEPARTMENT
•Department identifier
•College
•Department head
•Scheduling coordinator
COURSE
•Course number
•Department
•Required of department major (y/n)
•Course description
SECTION
•Section identification number
•Semester
•Year
•Classroom
•Start time
•End time
•Days of week for class meetings
•Employee identification number
•Name
•Address
•Birthdate
•Office telephone
•Social Security number
STUDENT
•Student identification number
•Name
•Address
•Birthdate
•Telephone
•Gender
•Ethic group
•Social Security number
OFFICE
•Office number
•Building
•Telephone extension
What other attributes may be
needed
 What needs to be added?
 What needs to be changed?
 What are common attributes that can be
used to “join” the tables?
 For class Thursday, have an idea of how
you think these entities could be
improved…we are going to spend some
time setting up a database
User’s View of a Computerized
Database
 Types of Data
 What is a Database?
 What is a File?
 Relational Databases
 Geographic Information Systems
Types of data…
 Formatted data items
 Text
 Images
 Audio
 Video
What is a database?
 A structured collection of items stored,
controlled and accessed through a computer
based on predefined relationships between
predetermined data types.
 What are some examples of databases that
you are familiar with?
 NOT a DBMS!
Files and records and fields...
 File
– A set of records
 Record
– A set of fields
 Field
– A group of characters with a predefined
meaning
 Key
– A field that uniquely identifies an entity
Relational Databases
 “A set of two-dimensional tables in which
one or more key-fields in each tables are
associated with corresponding key or nonkey fields in other tables.”
 Normalization
– eliminating redundancies from tables in the
database
 Typically accessed via SQL
Other types of databases
 Geographical Information Systems
– becoming quite important for county and local
governments
– Locally, Orange County and the Town of
Chapel Hill are looking for ways to integrate
GIS data with their information systems
 Image/video databases
Database Management Systems
 Defining the Database
 Methods for Accessing Data in a Computer
System
 Processing Transactions
 Controlling Distributed Databases
 Backup and Recovery
So…what is a DBMS?
 Examples
– Oracle
– Sybase
– Access
 Makes data more of an enterprise resource
and makes programming work more
effective/efficient
Defining the database and Access
to Data
 Data definition
– kept in a data dictionary
• Metadata (data about data!)
– Data definition for a database is a schema
 DBMS Access
– typically will be some form of indexed access
– sometimes, sequential access is useful
• less flexible
– controlled by the DBMS to minimize complexity
Indexed access
Transaction processing
 Small section in the book, but very
important
–
–
–
–
provides control for logical units of work
locks resources
manages concurrency
provides queuing and prioritization
 Can be in the DBMS or a separate
transaction server
Controlling Distributed
Databases
 Replication
– decentralized storage of information
 Two-phase commit
– maintain consistency
– try to protect data from network or system
failures
Backup and recovery
 Backup is often neglected
 Disaster recovery plans are often non-
existent
– Why do you need a disaster recovery plan?
– What is in such a plan?
Review of things covered so far...
 A model for describing information in a
system and the relationships
– the ERD
 What is a database?
 What is a DBMS?
 What is a transaction processing system?
 What about backup and recovery?
Hands-on Lab: Building a
database
 Use your modified table 4.2 (from Alter,
page 113)
 Create tables in Access for the entities
 Establish appropriate relationships
 Populate with sample information
Text Databases and Hypertext
 Hypertext
 Browsers
 Indexes and Search Engines
Hypertext
 Most common example today is HTML
– HyperText Markup Language
 Web combines hypertext and multimedia to
be a “hypermedia” system
 Let’s look at some HTML
– This may be a review for many, but bear with
us so we can all reach a common level of
understanding
The HTML for our class main
page
<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="GENERATOR" content="Mozilla/4.7 [en] (Win98; I) [Netscape]">
<meta name="Author" content="Joel Dunn">
<title>INLS60, Fall 2000</title>
</head>
<body bgcolor="#FFFFFF">
<center>School of Information and Library Science
<br>University of North Carolina at Chapel Hill</center>
<center>
<h2>
INLS60<br>
Information Systems Analysis and Design<br>
Fall 2000</h2></center>
<center>Tuesday/Thursday 2:00-3:15PM
<br>307 Manning
<br>Joel Dunn
<br>joel_dunn@unc.edu
<br>Office - 440 W. Franklin St., Rm. 07
<br>Phone: Office - 966-5837; Home - 968-1911
<p><a href="F00-Syllabus.html">Syllabus</a> / <a href="F00-Calendar.html">Calendar</a>
/ <a href="F00-Assignments.html">Assignments</a> / <a href="F00-Comm.html">Communications</a></center>
<p>
<hr ALIGN="CENTER"><b>Course Description:</b>
<p>Analysis of organizational problems and how information systems can
be designed to solve those problems. Application of database and interface
design principles to the implementation of information systems.
<p>
<hr ALIGN="CENTER">
<p><i>Last modified 3 August, 2000</i>
<br><i><a href="mailto:joel_dunn@unc.edu">Joel Dunn</a></i>
</body>
</html>
How does the browser fit in?
 Retrieve pages from the text databases of Web
servers
 Act as today’s defacto standard terminal for other
types of database access
– http://bullhead.ais.unc.edu/cgibin/waisretrieve.pl?1301425xxx1303956xxx/home/longlegs/flyfish/log00/
log0001d.txt:flyfish00
 Provide vector to launch applets
 Provide access to servlets
 Both applets & servlets are used for data access
Overview of Java Servlets
J
a
v
a
S
e
r
v
l
e
t
s
M
/
PL
W
M
/ L
W
N
a
m
e
:
S
m
i
t
h
S
S
N
:
1
1
1
2
2
3
3
3
3
E
n
t
e
r
C
l
i
e
n
t
i
m
p
o
r
t
j
a
v
a
x
.
s
e
r
v
l
e
t
.
*
;
c
l
a
s
s
M
y
S
e
r
v
l
e
t
e
x
t
e
n
d
s
G
e
n
e
r
i
c
S
e
r
v
l
e
t
{
p
u
b
l
i
c
v
o
i
d
s
e
r
v
i
c
e
(
S
e
r
v
l
e
t
R
e
q
u
e
s
t
r
e
q
u
e
s
t
,
S
e
r
v
l
e
t
R
e
s
p
o
n
s
e
r
e
s
p
o
n
s
e
)
t
h
r
o
w
s
S
e
r
v
l
e
t
E
x
c
e
p
t
i
o
n
,
I
O
E
x
c
e
p
t
i
o
n
{
.
.
.
}
}
W
e
b
S
e
r
v
e
r
P
r
o
g
r
a
m
t
h
a
t
r
u
n
s
o
n
W
e
b
S
e
r
v
e
r
,R
e
g
i
s
t
e
r
e
d
w
i
t
h
W
e
b
S
e
r
v
e
r
N
o
g
r
a
p
h
i
c
a
lU
s
e
r
I
n
t
e
r
f
a
c
e
(
H
T
M
L
)
L
e
s
s
r
e
s
o
u
r
c
e
i
n
t
e
n
s
i
v
e
t
h
a
n
C
G
Ip
r
o
g
r
a
m
s
(
l
o
a
d
o
n
c
e
,r
u
n
m
a
n
y
)
P
o
r
t
a
b
l
e
t
o
o
t
h
e
r
W
e
b
S
e
r
v
e
r
s
,p
o
s
i
t
i
o
n
i
n
g
f
o
r
f
u
t
u
r
e
E
J
B
s
P
a
r
t
o
f
J
D
K
1
.
1
a
s
a
S
t
a
n
d
a
r
d
J
a
v
a
E
x
t
e
n
s
i
o
n
A
P
I
(
G
e
n
e
r
i
c
S
e
r
v
l
e
t
,H
T
T
P
S
e
r
v
l
e
t
c
l
a
s
s
)
C
a
n
b
e
p
r
o
g
r
a
m
m
e
d
t
o
a
c
c
e
s
s
e
x
i
s
t
i
n
g
a
p
p
l
i
c
a
t
i
o
n
s
,
d
i
s
t
.o
b
j
e
c
t
s
,e
t
c
.
C
a
n
b
e
u
s
e
d
t
o
i
m
p
r
o
v
e
e
n
d
t
o
e
n
d
p
e
r
f
o
r
m
a
n
c
e
C
a
n
b
e
u
s
e
d
t
o
a
d
d
r
e
s
s
f
i
r
e
w
a
l
lc
o
n
c
e
r
n
Let’s review the basic model of
browser/server interaction
Indexes and search engines
 In the web context, what is an index?
 What does a search engine do?
– How is a search engine like a DBMS?
 How has the pervasiveness of hypertext and
web-based searching changed the way we
deal with collections of information?
 What are your favorite search engines, and
why?
Evaluating Information Used in
Business Processes
 Information Quality
 Information Accessibility
 Information Presentation
 Information Security
Information quality
INFORMATION QUALITY
•ACCURACY
•PRECISION
•COMPLETENESS
•AGE
•TIMELINESS
•SOURCE
•What are some examples of
these qualities?
Information accessibility,
presentation and security
INFORMATION ACCESSIBILITY
•AVAILABILITY
•ADMISSIBILITY
INFORMATION PRESENTATION
•LEVEL OF SUMMARIZATION
•FORMAT
INFORMATION SECURITY
•ACCESS RESTRICTION
•ENCRYPTION
Let’s think about a database and
evaluate it based on these criteria
 What about your academic record, your
history of courses taken and grades received
here at UNC?
Models as Components of
Information Systems
 Mental Models and Mathematical Models
 What-if Questions
Models…
 A part of the decision making process
A mental model…how you think
things work...
Mathematical model
 Series of equations/algorithms that describe
relationships between variables
 Is often an instantiation of a mental model
in an information system to apply data to
solve a problem
What-if Questions
 Enabled by mathematical models
 How things could operate given a change in
circumstances
 Discussion item…
– how might we try to build a model to examine
the impact of dramatically increased enrollment
at UNC over the next 10 years? What elements
would we put in our model; what would we
exclude?