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)
DEPARTMENT•Department identifier•College•Department head•Scheduling coordinatorCOURSE•Course number•Department •Required of department major (y/n)•Course descriptionSECTION•Section identification number•Semester•Year•Classroom•Start time•End time•Days of week for class meetings
PROFESSOR•Employee identification number•Name•Address•Birthdate•Office telephone•Social Security numberSTUDENT•Student identification number•Name•Address•Birthdate•Telephone•Gender•Ethic group•Social Security numberOFFICE•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 non-key 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>[email protected]<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 canbe designed to solve those problems. Application of database and interfacedesign principles to the implementation of information systems.<p><hr ALIGN="CENTER"><p><i>Last modified 3 August, 2000</i><br><i><a href="mailto:[email protected]">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/cgi-bin/waisretrieve.pl?1301425xxx1303956xx
x/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 ServletsJava Servlets
LM/W
P L
M/W
Web ServerClient
Name: SmithSSN: 111-22-3333
Enter
import javax.servlet.*;class MyServlet extends GenericServlet { public void service( ServletRequest request, ServletResponse response ) throws ServletException, IOException {...}}
Program that runs on Web Server, Registered with Web ServerNo graphical User Interface (HTML)Less resource-intensive than CGI programs (load once, run many) Portable to other Web Servers, positioning for future EJBsPart of JDK 1.1 as a Standard Java Extension API
(GenericServlet, HTTPServlet class)Can be programmed to access existing applications, dist. objects, etc.Can be used to improve end-to-end performanceCan be used to address firewall concern
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?