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The System Life Cycle

Learn about system analysis, user-centered design, and complex system management. Explore Waterfall, Spiral, and Rapid Prototyping models. Discover integrated library systems and management concerns. Also, delve into requirements, testing, and alternative architectures in IT.

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The System Life Cycle

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  1. The System Life Cycle Week 14 LBSC 690 Information Technology

  2. Agenda • Questions • Systems analysis • Building complex systems • Managing complex systems • Final exam review

  3. 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?

  4. 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

  5. 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?

  6. 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)

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

  8. Discussion Point:Integrated Library System • What functions should be integrated? • What are the key data flows? • Which of those should be automated?

  9. 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

  10. 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

  11. The Waterfall Model Requirements Specification Software Test Plan

  12. 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, …)

  13. The Spiral Model 2.3 1.2 0.5 1.1 2.2 1.0 2.1 2.0 3.0

  14. Some Unpleasant Realities • The waterfall model doesn’t work well • Requirements usually incomplete or incorrect • The spiral model is expensive • Redesign leads to recoding and retesting

  15. 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

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

  17. 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

  18. 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

  19. 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

  20. Hands On: What Goes Wrong? • Check out Risks Digest for a random date • http://groups.google.com/groups?q=comp.risks • Pick a random date near your birthday • Find a case of unexpected consequences • Try to articulate the root cause • Not the direct cause

  21. Discussion Points:Managing Complex Systems • Critical system availability • Why can’t we live without these systems? • Understandability • Why can’t we predict what systems will do? • Nature of bugs • Why can’t we get rid of them? • Auditability • How can we learn to do better in the future?

  22. 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 Critical Infrastructure Protection SCADA: Supervisory Control and Data Acquisition

  23. 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

  24. 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

  25. 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 Bentley’s

  26. Computers Web Networks Search XML Integration Interaction Multimedia Midterm Communication Programming Project Policy Databases Final Life Cycle The Grand Plan

  27. Computer Systems • Hardware • Types of hardware • Storage hierarchy • Moore’s law • Software • Types of software • Types of interfaces

  28. 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

  29. Structured Documents • The Web • HTTP, HTML, URL • XML • DTD, XSL, XLink My Browser

  30. Multimedia • Compression, compression, compression • Images: Lossy vs loseless • Video: Frames are alike • Speech: Predictable characteristics • Music: Masking • Streaming Media Sever Buffer Internet

  31. Programming • Balancing machines and human needs • Machines require low-level specific instructions • Humans require high-level abstraction • Object models represent aspects of reality • Can create any behavior from 3 control structures • Sequential execution • Conditional • Iteration • Javascript interpreters are in Web browsers

  32. Databases • Structured information • Field->record->table->database • Primary key • Normalized tables (relations) • Remove redundancy, inconsistency, error • “Join” links tables • Foreign key • Visual programming in Access

  33. Integration • Multimedia • SMIL • Web-accessible databases • Cold Fusion

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

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

  36. Human-Computer Interaction • Human-machine synergy • Mental models • Input and output devices • Interface types • Direct manipulation, menu, language based

  37. Computer-Mediated Communication • Synchronous / Asynchronous • Remote / local • One-to-one / many-to-many • Computer-Supported Cooperative Work • Computers as educational media

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

  39. Life Cycle • Systems analysis • Software development models • Managing complex systems

  40. R.J. Bentley’s Filling Station Monday Dec 15, 2003 at 8:00 P.M.

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