The%20System%20Life%20Cycle

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The System Life Cycle

• Week 14
• LBSC 690
• Information Technology

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Agenda

• Questions
• Systems analysis
• Building complex systems
• Managing complex systems
• Final exam review

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The System Life Cycle

• Systems analysis
• How do we know what kind of system to build?
• User-centered design
• How do we discern and satisfy user needs?
• Implementation
• How do we build it?
• Management
• How do we use it?

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Systems Analysis

• First steps
• Understand the task
• Limitations of existing approaches
• Understand the environment
• Structure of the industry, feasibility study
• Then identify the information flows
• e.g., Serials use impacts cancellation policy
• Only then can you design a solution

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Analyze the Information Flows

• Where does information originate?
• Might come from multiple sources
• Feedback loops may have no identifiable source
• Which parts should be automated?
• Some things are easier to do without computers
• Which automated parts should be integrated?
• What other systems are involved?
• And what information do they contain?

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Analyzing Information Flows

• Process Modeling
• Structured analysis and design
• Entity-relationship diagrams
• Data-flow diagrams
• Object Modeling
• Object-oriented analysis and design
• Unified Modeling Language (UML)

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Some Library Activities

• Acquisition
• Cataloging
• Reference
• Online Public Access Catalog (OPAC)
• Circulation
• Weeding
• Reserve, recall, fines, interlibrary loan,
• Budget, facilities schedules, payroll, ...

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Discussion PointIntegrated Library System

• What functions should be integrated?
• What are the key data flows?
• Which of those should be automated?

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User-Centered Design

• Start with user needs
• Who are the present and future users?
• How can you understand their needs?
• Evaluate available technology
• Off-the-shelf solutions
• Custom-developed applications
• Implement something
• Evaluate it with real users

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The Waterfall Model

• Key insight invest in the design stage
• An hour of design can save a week of debugging!
• The motivation behind DoD Standard 2167
• Requirements
• Specifies what the software is supposed to do
• Specification
• Specifies the design of the software
• Test plan
• Specifies how you will know that it did it

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The Waterfall Model
Requirements
Specification
Software
Test Plan
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The Spiral Model

• Build what you think you need
• Perhaps using the waterfall model
• Get a few users to help you debug it
• First an alpha release, then a beta release
• Release it as a product (version 1.0)
• Make small changes as needed (1.1, 1.2, .)
• Save big changes for a major new release
• Often based on a total redesign (2.0, 3.0, )

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The Spiral Model
2.3
1.2
0.5
1.1
2.2
1.0
2.1
2.0
3.0
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Some Unpleasant Realities

• The waterfall model doesnt work well
• Requirements usually incomplete or incorrect
• The spiral model is expensive
• Redesign leads to recoding and retesting

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The Rapid Prototyping Model

• Goal explore requirements
• Without building the complete product
• Start with part of the functionality
• That will (hopefully) yield significant insight
• Build a prototype
• Focus on core functionality, not in efficiency
• Use the prototype to refine the requirements
• Repeat the process, expanding functionality

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Rapid Prototyping Waterfall
Update Requirements
Write Specification
Choose Functionality
Initial Requirements
Create Software
Build Prototype
Write Test Plan
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Implementation Requirements

• Availability
• Mean Time Between Failures (MTBF)
• Mean Time To Repair (MTTR)
• Capacity
• Number of users for each application
• Response time
• Flexibility
• Upgrade path

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Alternative Architectures

• Batch processing (e.g., recall notices)
• Save it up and do it all at once
• Timesharing (e.g., OPAC)
• Everyone uses the same machine
• Client-Server (e.g., Web)
• Some functions done centrally, others locally
• Peer-to-Peer (e.g., Kazaa)
• All data and computation is distributed

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Management Issues

• Retrospective conversion
• Even converting electronic information is
  expensive
• Management information
• Peak capacity evaluation, audit trails, etc.
• Sometimes costs more to collect than it is worth!
• Training
• Staff, end-users
• Privacy

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Hands On What Goes Wrong?

• Check out Risks Digest for a random date
• http//catless.ncl.ac.uk/Risks
• Pick a random date near your birthday
• Find a case of unexpected consequences
• Try to articulate the root cause
• Not the direct cause

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Discussion PointsManaging Complex Systems

• Critical system availability
• Why cant we live without these systems?
• Understandability
• Why cant we predict what systems will do?
• Nature of bugs
• Why cant we get rid of them?
• Auditability
• How can we learn to do better in the future?

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Critical Infrastructure Protection

• Telecommunications
• Banking and finance
• Energy
• Transportation
• Emergency services

• Food and agriculture
• Water
• Public health
• Postal and shipping
• Defense industrial base
• Chemical industry and hazardous materials

SCADA Supervisory Control and Data Acquisition
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National Cyberspace Strategy

• Response system
• Analysis, warning, response, recovery
• Threat and vulnerability reduction
• Awareness and training program
• Return on investment, best practices
• Securing government systems
• International cooperation

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Summary

• Systems analysis
• Required for complex multi-person tasks
• User-centered design
• Multiple stakeholders complicate the process
• Implementation
• Architecture, open standards,
• Management
• Typically the biggest cost driver

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Talk to Me About the Exam!

• About 5 questions
• Same question styles as the midterm
• Some may require use of the computer
• Comprehensive - covers the entire course
• Emphasis and structure from the second half
• Two hours
• Post-exam discussion at Bentleys

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The Grand Plan
Interaction
Quiz
Midterm
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Computer Systems

• Hardware
• Types of hardware
• Storage hierarchy
• Moores law
• Software
• Types of software
• Types of interfaces

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Networks

• Types of Networks
• LAN, WAN, Internet, Wireless
• Packet Switching
• Ethernet, routers, routing tables
• Layered Architecture and protocols
• TCP/UDP
• IP address/domain name
• Encryption

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Structured Documents

• The Web
• HTTP, HTML, URL
• XML

My Browser
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Multimedia

• Compression, compression, compression
• Image lossy vs loseless
• Video frames are alike
• Speech voice predictable
• Music masking
• Streaming

Media Sever
Buffer
Internet
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Human-Computer Interaction

• Human-machine synergy
• Mental models
• Input and output devices
• Interaction styles
• Direct manipulation, menu, language based

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Programming

• Programming languages
• Machines require low-level specific instructions
• Humans require high-level abstraction
• Can create any behavior from 3 control structures
• Sequential execution
• Conditional
• Iteration
• Javascript interpreters are in Web browsers

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Databases

• Structured information
• Field-gtrecord-gttable-gtdatabase
• Primary key
• Normalized tables (relations)
• Remove redundancy, inconsistency, error
• Easy update, search
• Join links tables together
• Through foreign key
• Access provides visual operations

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Web-Database Integration

• Access Data Access Pages
• PHP
• SQL

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Computer-Mediated Communication

• Synchronous / Asynchronous
• Remote / local
• One-to-one / many-to-many
• Computer-Supported Cooperative Work

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The Web

• Huge, dynamic, redundant, and diverse
• Multimedia, multilingual, multicultural
• Deep Web
• Internet Archive

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Search

• Exact match
• Term-based ranked retrieval
• Recommender systems
• Web search
• Links and anchor text
• Evaluation

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Policy

• Ownership
• Equitable access
• Controlled access
• Identity
• Choosing good passwords
• Privacy
• Government / commercial
• Integrity

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Life Cycle

• Systems analysis
• Software development models
• Managing complex systems

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R.J. Bentleys Filling Station
Thursday Dec 15, 2005 at 830 P.M.