Chapter 4Information 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>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 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: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/cgi-bin/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 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?