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ORIE 480 Study Sheet: MIDTERMJames YuJane Thipphavong

Lecture 1: Database Systems Intro Data: Raw facts that are described, observed, or measured

Information: Data that has been organized or prepared

Knowledge: Data/Information/Rules that are used for actual decision making

Database Management System (DBMS): A collection of programs that

define/manipulate/maintain databases

Database: A collection of interrelated data

File Systems are unattractive

o Data-program dependence: must write custom programs to query

o Redundancy

o Inconsistency

o Lack of securityo Have to write your own

o If a query has not been foreseen, an expert programmer is needed

Different types of DBMS

o Hierarchical

o Network

o Relational

o Object-oriented

Database Tables Restrictions

o Columns contain same type of data

o One value per cell

o One (or more) column(s) contains a unique value for each row

Primary Keyo Rows have the same size (# of columns)

Order is unimportant, and are dynamic

Transactions

o Logical unit of access to a DBMS

o Concurrency and Recovery from system crashes

o Locks, Write-Ahead Logs and Checkpoints

2 Components of RDBMS

o Data Definition Language (DDL)

Allows you to define metadatao Data Manipulation Language (DML)

Allows you to insert/edit/delete/ask questions about data

QBE, SQL

Lecture 2: Designing Databases Entity-Relationship Diagrams Entities: things about which one wants to store info

Attributes: the info one wants to store about the entity

Relationships: Associations between two or more entities

Cardinality: 1:1, 1:N, N:M

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Participation

o Total Participation: every student must have an advisor

o Partial Participation: a professor may not be teaching any classes

o Circle: Denotes partial participation for the opposing box (think race relations

and throwing the balls)

o Referential Integrity:A database entry should refer to something that exists

Weak Entity: Part of its key is in another entity

Primary Key: An attribute that uniquely determines a record

Foreign key: An attribute in one entity which is the primary key of another entity to which

the table is related

Mapping ERDs to Tables

o 1:1

Put the primary key of 1 entity to the table of the other 1 entityo 1:N

Put the primary key of 1 entity to the table of the N entityo N:M

Create new table consisting of primary keys of both tables

Lecture 3: WWW Client Server Model

o Client opens a connection, makes a request

o Server returns file

o Connection closed

WWW runs on HyperText Transfer Protocol

o GET requests an item

o HEAD requests information about an item (then check if stored in cache)

Many IT systems and definitely the WWW are too large for a person to use effectively, so

develop searching tools

Lecture 4: Query by Example and SQL Done by Examples

Lecture 5: Internet Markup Languages and Regular Expressions HTML

o Very simple

o Fail-soft principle: If your tags are wrong, something still appears

o Apply formatting tags to basic elements

o Meta tags provide information

o Structural versus formatting tags

SGML

o

Standard generalized markup languageo What HTML is based on, pre-defined tags

XML

o eXtensible Markup Language fordescribinginformation

o user-defined tags

o extensibility

o precise structure

o valid Document Type Definition (DTD)

DTD is a grammar for the XML document

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o eXtensible Stylesheet Language (XSL)

o XML is becoming the standard front end of databases on the Web

o DBMS are incorporating XML output capabilities

Lecture 6 and 7: Networkso Circuit Switched: end systems are connected to senders by an end-to-end reserved

circuit.

o Datagram Networks: Every packet has full addressing information, and can be routed

independently of others.

o Layers of Networks: Host -> TCP or UDP -> IP -> Subnetwork -> Physical Media

o An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP

protocol route messages based on the IP address of the destination. The format of an IPaddress is a 32-bit numeric address written as four numbers separated by periods. Eachnumber can be zero to 255. For example, 1.160.10.240 could be an IP address.

o UDP: User Datagram Protocol,

o Demuxing layer

o In order to know which process to send the packet to (email, ftp, ,telnet, web, etc)

o TCP (Transmission Control Protocol)

o Packet Sequencingo Flow control

o Domain Name System (DNS): distributed Internet directory service. DNS is used mostly

to translate between domain names and IP addresses, and to control Internet emaildelivery. Most Internet services rely on DNS to work, and if DNS fails, web sites cannotbe located and email delivery stalls.

o Email: Client sends to Sendmail server, which sends to Mail Transfer Agent (MTA), which

queries the DNS and sends to the destination MTA, which sends to the destinationGetmail server, and finally to the receiving client.

o Firewalls

o Kind of router

o Prevents unwanted packets from entering a site

o

Hackers could still hack into the mail server and gain access to siteo DMZ (Demilitarized Zones) evolved let mail server reside outside firewall to

prevent hackers from gaining access to site through mail server (and other suchservers)

o IP Address Distribution Problem

o Improve the efficiency of address assignment

o Design a new IP with more address space

o Dynamic IP address assignment

o Network Address Translation; Gives hosts non-global addresses and translates

them to global addresses on the flyo Virtual Private Network (VPN)

o The concept of including a node in a public network (internet) into a sites private

networko Using tunneling and encryption for security

o Dial-up Roaming

o ISPs having roaming agreements with other ISPs via a common mediator

o Allows you to access your ISP in many different cities around the country

Lecture 8: Dynamic and Active Web Technologieso Static: a file resides on the web server

o Pros: cheap and fast

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o Cons: inflexible, revisions are hard, may need many documents compared to

dynamic

o Dynamic: document is created upon request (by server)

o Pros: flexible; current

o Cons: uses server resources, slower, costly to create and debug; cant display

changing information; security issues for the server

o State Information Information that program saves between invocations

o Active: Server returns a program which runs in users browser

o Pros: flexible

o Cons: Costly and difficult to create and debug; security risk for the client

o Java active documents are called applets

o Javascript: browsers read and interpret javascript embedded in html

Lecture 9: Introduction to Decision Analysis Goal: Make decisions

o Well grounded probability

Probability

o P(A|B) = P(AB) / P(B)

Lecture 10: Decision Analysis Biases Human Limitations on Information Processing

o Short-term memory

o Unreliable recall of information

o Slow numerical calculations

o Inaccuracy from Biases

Two Models of Decision Making

o Fully Rational Approach

Requires complete, perfect, and instantaneous information

Requires solution to hard computational problems

Rationality = Expected utility maximization

o Satisficing (bounded-rational) approach

Use of limited amount of information, heuristics

Heuristics

o Availability Heuristics

What is easily recalled must be most likely

Biases

Ease of recall

Retrievability

o Representativeness Heuristics

Beliefs about what are representative examples of particular groups of

events Biases

Insensitivity to base rates

Misconceptions of chance

o Anchoring and adjustment heuristics

Starting somewhere and adjusting

Biases

Over reliance on initial guess and overconfidence

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Decision Analysis

o Advantages

Models rich problem structure

Well grounded in theory

Formal methods to compute optimal solutions

Avoids human biases

Sensitivity analysis

o Disadvantages

Abstract model: may be to simple

Uncertainty can still exist

Model can include biases

Size and complexity of model can become horrendous

Lecture 11: Decision Trees Maximax: Choose decision that yields maximum profit

Maximin: Choose decision that would make you lose the least amount of money

Regret Matrix: Difference in the amount of profit if you had chosen

Least Regret Decision: Choose decision that generates least amount of regret in any

case

Decision Tree

o Solving a Decision Tree

Compute the posterior conditional probabilities

Ie. P(good market | forecast good)

Compute the values at the outcome nodes

Work back from outcome nodes towards the root node

Read off the optimal decision at teach decision nodeo Advantages

Structures a decision process

Evaluates all possible outcomes

Decision making process is succinct

Focuses decision on financial figures, probability, and assumptions

Sensitivity analysis

Lecture 12: Information Systems in Enterprises Information Architecture Structure

o Hierarchy of Levels

Strategic

Management

Knowledge

Operationalo Departments

Sales and Marketing

Finance

Accounting

Manufacturing

Human Resourceso IT Infrastructure

Hardware

Software

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Data and Storage

Networkso 6 Major types of Information Systems

Executive Support Systems (ESS) (Strategic Level)

Management Information Systems (Management Level)

Decision Support Systems (Management Level)

Knowledge Work Systems (Knowledge Level) Work Stations (Knowledge Level)

Transaction Processing Systems (Operational Level)

OLTP

o A type of computer processing in which the computer responds immediately to

user requests. Each request is considered to be a transaction. Automatic tellermachines for banks are an example of transaction processing.

o ACID test

Atomicity (all or nothing)

Consistency (The database is transformed from one valid state toanother valid state.)

Isolation (The results of a transaction are invisible to other transactions

until the transaction is complete) Durability (Once committed (completed), the results of a transaction are

permanent and survive future system and media failures)

Batch

o The opposite of transaction processing is batch processing, in which a batch of

requests is stored and then executed all at one time. Transaction processingrequires interaction with a user, whereas batch processing can take place withouta user being present.

MIS issues

o Multiple entries of same data

o Multiple versions of the same element

o Conflicting data definitions

o

Nonstandard systems interfaceso Data glut

o Inflexibility

o Report writing backlog

o Data ownership and hoarding

o Lack of timeliness

Business Processes

o Before: Stovepipe Systems

o After: Enterprise System

On Line Analytical Processing

o a key reporting and analysis tool for operations and strategic planning

o Query-driven, usually over multidimensional DB

o most OLTP systems unsuitable for OLAP: OLTP will slow down OLAP

Data Warehouses

o Source of data for OLAP

Includes analytical toolso Key enabler is Metadata

Identifies the technical aspects of the data

Identifies the business meaning of the data

Provides utilization tools

Data Mining

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Lecture 14: MIS Design and Implementation- Key Components of Systems Analysis

o Decisions

o Transactions and Processing

o Information and its flow

o Individuals and functions involved

o Communications and coordination- Systems life cycle

o Inception

o Systems analysis

o Feasibility Study

o Design

o Specifications

o Building the system

o Testing

o Training

o Conversion & Installation

o Maintenance & Enhancements

-Critical Success Factors

o A small number of objectives on which IS must focus

o Attention on how things should be

- Data Collection for Analysis and Designo Observation

o Interview

o Questionnaires

- Design Methodologieso Structured (e.g. Data flow diagrams)

o Objected Oriented Model (UML: universal modeling language)

- Testing- Conversion

o Parallel Strategy: run both old and new system

o Direct cutover: kill old system and use new oneo Pilot Study: implement new system in one part of company

o Phased Approach: intro system in stages instead of all at once

- Training and Documentation- User-oriented Design

o Use of prototypes

o Prototypes are quickly made and have flexible design

- Outsourcingo Advantages

May pay only what you use

Access to top talent

Frees up company resourceso

Disadvantages Underestimate cost of finding and evaluating vendors

Monitoring

Loss of control- Causes of successes and failures

o Funding

o Insufficient user involvement

o User-Designer communications gap

o Insufficient management support

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o Level of complexity

Project size

Project structure

Experience with technologyo Politics

o Non-systematic approach to changes