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Systems Design

Systems Design. We we came from…. Identify Problem/Value. Feasibility Analysis. Project Management. Planning. Understand as-is system. Identify Improvements. Develop concept for the to-be system. Use Cases. DFDs. ERDs. Analysis. Design. Implementation. Systems Design.

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Systems Design

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  1. Systems Design

  2. We we came from… Identify Problem/Value. Feasibility Analysis. Project Management. Planning Understand as-is system. Identify Improvements. Develop concept for the to-be system. Use Cases. DFDs. ERDs. Analysis Design Implementation

  3. Systems Design Develop technical specifics for to-be system. Design Strategies. Physical DFD. Physical ERD. Infrastructure Plan. Interface Structure. Interface Standards. Interface Template. Interface. Evaluate. Planning Analysis Design Implementation

  4. Design Strategy: Outsource or not? • Factors Favoring Make • Customized Products • Confidentiality of Data & Business • Reduce Vendor Risk • Increased Ease of Development • Ease of Internal Adaptation of Software • Develop Leading-Edge Competence • Factors Favoring Buy • Access to Specialized Skills • Cost • Staff Utilization • Reduced Recruitment & Training • High Standards of Control & Security • Proliferation of Information Services

  5. Outsource? Check SDLC Systems Investigation Product: Feasibility Study Understand the Business Problem or Opportunity Highly Structured Systems Analysis Product: Functional Requirements Develop an Information System Solution Systems Design Product: System Specifications OR... Systems Implementation Product: Operational System Implement the System Solution Most time spent here. Systems Maintenance Product: Improved System

  6. Infrastructure Plan: Centralizedor Distributed? Dumb Dumb Dumb Dumb Dumb

  7. Infrastructure Plan: Centralizedor Distributed?

  8. Tiers in a Client-Server Network Tier One: Main Server Tier Two: Clients of Tier One, Servers to Tier Three Tier 3: Clients of Tier Two

  9. How are infrastructures established? A quick look at Telecomm Basics. Let’s talk:

  10. I want to talk to someone else:

  11. They want to talk to someone else etc., etc.!!!:

  12. Along comes the switch. In Public Switched Telephone Network (PSTN, or sometimes “POTS”), this is basically the EXCHANGE (last 4 digits) CO Switch (aaa) ppp-XXXX

  13. Switches in the same LATA (“Local Access and Transport Area”) are distinguished by PREFIX (first 3 digits). (aaa) PPP-xxxx

  14. Calls that cross a LATA boundary are distinguished by AREA CODE (numbers in parentheses). These are “long distance” calls. LATA boundary (AAA) ppp-xxxx

  15. PSTN • These calls are all “circuit switched” • Dedicated line. • Comes from voice requirements. • Contrasts the Internet and Web which is “packet switched”. • Messages can travel many paths. • Comes from data requirements.

  16. E-mail from Company A to Company D: Company B 01001 W9 11001 01011 11110 W7 W6 W8 Company A Company D Internet Backbone W2 W1 W11 W12 W3 W5 W4 Company C W10

  17. E-mail from Company A to Company D: Company B W9 W7 W6 W8 01001 Company A Company D 11001 Internet Backbone W2 W1 W11 W12 01011 11110 W3 W5 W4 Company C W10

  18. E-mail from Company A to Company D: broken into packets, that travel the best path. Company B W9 W7 01011 W6 01001 W8 Company A Company D Internet Backbone W2 W1 W11 W12 11110 W3 W5 11001 W4 Company C W10

  19. E-mail from Company A to Company D: packets reassembled at the other end. Company B Of course, TCP/IP is the dominant packet switching protocol. W9 W7 W6 W8 01001 Company A Company D 11001 Internet Backbone W2 W1 W11 W12 01011 11110 W3 W5 W4 Company C W10

  20. Putting it all together. Company B Companies A-D are all connected to the Internet, Companies B & D are trading partners and are connected through a WAN, and Consumers 1 & 2 are connected to the PSTN, and also to the Internet through the PSTN. A "W" in a box represents a Web server (thus, Company D's Web server is "W12") . W9 WAN W7 W6 W8 Company A Company D Internet Backbone W2 W1 W11 W12 W3 W5 W4 PSTN Company C W10 Consumer 1 Consumer 2

  21. firewall, fiber, frame relay, TCP/IP, DSL, and modem? Company B W9 WAN W7 W6 W8 Company A Company D Internet Backbone W2 W1 W11 W12 W3 W5 W4 PSTN Company C W10 Consumer 1 Consumer 2

  22. What about wireless? “Cells” Base Stations “Mobile Telephone Switching Office” MTSO PSTN Mobile Units Other Base Stations MTSO

  23. Microwave Link Microwave Link Earth Station Earth Station Multiplexer Satellite Regional Office Modem Satellite Central Office Fiber optic cable Coaxial cable Wireless LAN Host Computer Gateway Multiplexer End User Workstation Telecommunications Infrastructure Satellite

  24. Infrastructure Plan • You must understand the available local, regional, national, and international infrastructure to make your plan!!! • Your plan determines your “options” for years to come!!! Don’t base your plan simply on your immediate needs.

  25. Systems Design Develop technical specifics for to-be system. Design Strategies. Physical DFD. Physical ERD. Infrastructure Plan. Interface Structure. Interface Standards. Interface Template. Interface. Evaluate. Planning Analysis Design Implementation

  26. Interface • The connection between the system and the rest of the world (whether humans or other systems). • “The interface **IS** the system.”

  27. Principles for User Interface Design • Layout • Content awareness • Aesthetics • User experience • Consistency • Minimal user effort

  28. Layout Concepts • The screen is often divided into three boxes • Navigation area (top) • Status area (bottom) • Work area (middle) • Information can be presented in multiple areas • Like areas should be grouped together

  29. More Layout Concepts • Areas and information should minimize user movement from one to another • Ideally, areas will remain consistent in • Size • Shape • Placement for entering data • Reports presenting retrieved data

  30. Minimize Effort • Three clicks rule • Users should be able to go from the start or main menu of a system to the information or action they want in no more than three mouse clicks or three keystrokes

  31. User Interface Design Process

  32. User Interface Design Process: Five Step Process

  33. Interface Evaluation Methods • Heuristic evaluation • Compare design to checklist • Walkthrough evaluation • Team simulates movement through components • Interactive evaluation • Users try out the system • Formal usability testing • Expensive • Detailed use of special lab testing

  34. User Interface Design Components • The navigation mechanism provides the way for users to tell the system what to do • The input mechanism defines the way the system captures information • The output mechanism defines the way the system provides information to users or other systems

  35. Navigational Design: Basic Principles • Assume users • Have not read the manual • Have not attended training • Do not have external help readily at hand • All controls should be clear and understandable and placed in an intuitive location on the screen.

  36. Navigational Design: Basic Principles • Prevent mistakes • Limit choices • Never display commands that can’t be used (or “gray them out”) • Confirm actions that are difficult or impossible to undo • Simplify recovery from mistakes • Use consistent grammar order

  37. Input Design: Basic Principles • The goal is to simply and easily capture accurate information for the system • Reflect the nature of the inputs • Find ways to simplify their collection • “Garbage in, garbage out” • Financial Example

  38. Online versus Batch Processing • Online processing immediately records the transaction in the appropriate database • Batch processing collects inputs over time and enters them into the system at one time in a batch • Batch processing simplifies data communications and other processes, but means that inventory and other reports are not accurate in real time

  39. Capture Data at the Source • Reduces duplicate work • Reduces processing time • Decreases cost • Decreases probability of error

  40. Interface Design Choices You have recently been promoted to IS manager of a fast-food chain. Your first assignment is to speed up the drive-through line, using a more modern method of user interface (currently drivers speak their orders to an employee of your chain). Your order process is PC-based. Discuss possible options.

  41. Source Data Automation • Can be obtained by using the following technologies: • bar code readers • optical character recognition • magnetic stripe readers • smart cards • Web • voice recognition?

  42. Output Design: Basic Principles • Understand report usage • Reference or cover-to-cover? • Frequency? • Real-time or batch reports? • Manage information load • All needed information, no more • Minimize bias

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