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SY DE 542

SY DE 542. Work Domain Analysis (cont’d) Information Requirements Jan. 17, 2005 R. Chow Email: chow@mie.utoronto.ca. WDA: Defining the System. What does the user want to control? What does the user want information on? Main: Troubleshooting by User Make Visible to User vs.

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SY DE 542

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  1. SY DE 542 Work Domain Analysis (cont’d) Information Requirements Jan. 17, 2005 R. Chow Email: chow@mie.utoronto.ca

  2. WDA: Defining the System • What does the user want to control? • What does the user want information on? Main: • Troubleshooting by User • Make Visible to User vs. Peripheral: - Troubleshooting by Other - Make Transparent to User

  3. Example: Power Generation & Delivery • Countrywide: • Plants, Electrical Grid, Energy Users • Plant: • Units, Storage, Internal Grid • Unit: • Generator, Turbines, etc.

  4. WDA: System Boundary • What to Include (Usually): • Things user can control, wholly or partly • Things that interact with user’s work domain • Things the user must monitor or supervise

  5. WDA: System Boundary • What to Exclude (Usually): • Databases • Sensors • Input and Output Devices • Human-Computer Interface • Software • Object of Design or Redesign

  6. WDA: Part-Whole Hierarchy • Decomposition of a system into subsystems, and subsystems into components … (from coarse -> fine) • # of levels is not fixed • A complete WDA has 2 dimensions: • Abstraction Hierarchy (along vertical) • Part-Whole Hierarchy (along horizontal) • Not every cell in this 2-dimensional space will be filled

  7. A Generic WDA coarse fine abstract/ functional Part-Whole Hierarchy Abstraction Hierarchy concrete/ physical

  8. Two-Dimensional WDA • Functional Purpose is generally associated with whole system • Physical Function is generally associated with individual components • Some representation at every level of each hierarchy • But no fixed number of cells to complete • May help to distinguish AND vs. OR

  9. DURESS Example (revisited) • 1 Water Source (temp fixed @ 10 deg C) • 2 Reservoirs • If overfilled, system shuts down • 2 Heaters • Each unique to a single reservoir • If an empty reservoir is heated, system blows up • 2 Redundant Feedwater Streams per Reservoir • Fws-A1 & Fws-B1; Fws-A2 & Fws-B2 • Pumps: ON / OFF • Valves: • Primary Input (VA & VB): 1-10 • Secondary Input (VA1, VA2, VB1, VB2): 1-10 • Output (VO1, VO2): 1-20 • Demanded Temperatures (constant): • 40 deg C for Res1; 20 deg C for Res2 • Demanded Supplies (dynamic): • Same or different for Res 1 and Res 2

  10. Functional Purpose • What was the work domain designed to do? • How do I know if it’s working correctly? • How do I know if it’s working well vs. poorly? Some checks: • Have I found at least two purposes? • What else is important besides performance? safety, efficiency, environment, profit? • Do my purposes hold across all possible tasks?

  11. DURESS: Functional Purpose • Temperature Goal • Output Goal • Temp1, Temp2, Output1, Output2

  12. Abstract Function • What laws cannot be broken? • What priorities must be achieved? • What flows through the system? What is conserved? • Mass, Energy, Information, Money, Unchangeable Resources

  13. DURESS: Abstract Function • Mass1, Mass2 • Energy1, Energy2 • How do you know when mass is conserved (or not)? • Mass Source, Inventory, Sink • When conserved, what is relationship? • When not conserved, what is relationship? • Likewise for energy: • Energy Source, Inventory, Sink

  14. Generalized Function • How are causal relationships implemented? • How are flows, conversions implemented? • Some processes to consider: • combustion, convection, radiation, conduction, evaporation, condensation, distillation, cracking, moving, launching, digestion, respiration (Hint: -ing; -ion) • What processes must user monitor? • NOT what processes must user do with interface! • e.g., monitoring, detecting, managing, reporting

  15. DURESS: Generalized Function • Mass is implemented as WATER • Energy is implemented as HEAT • Subsystem Level: • Heat and Water Injection • Water Holding System • Heat Holding System • Heat Transfer System • Heat and Water Removal • Component Level • Pump Flow, Valve Flow • Water Holding Tank • Heat Holding Tank • Heat Transfer • Valve Flow

  16. Physical Function • What are the components? • What are their capabilities? • How are they involved in the processes? • (Hint: capabilities usually have limits)

  17. DURESS: Physical Function • Pumps (PA, PB) • Capability: On / Off • Input Valves (VA, VB, VA1, VA2, VB1, VB2) • Capability: 0-10 units/time • Reservoirs (R1, R2) • Capability: 1-100 units; 0-100 deg C • Heaters (H1, H2) • Capability: 0-10 setting • Output Valves (VO1, VO2) • Capability: 0-20 units/time

  18. DURESS: Physical Form • Location and Appearance of: • PA, PB, VA, VB, VA1, VB1, VA2, VB2, VO1, VO2, R1, R2, H1, H2

  19. Physical Form • What does the work domain look like? • What are the sizes, locations, colours, shapes, locations, conditions, materials of the components? • Not every attribute of every component needs to be included – think about how info will be used! • Potential Uses • Icon • Video • Detailed Drawings • Layout and Connections

  20. WDA: Recommended Approach • Define the System • Start from Top of AH • >= 2 purposes? • evaluation criteria? • Next, work from Bottom • All available resources and equipment? • Form and Function? • No interface? No controller? • Complete Middle • AF: causal laws, conservation principles • GF: more concrete processes

  21. WDA: Important Checks • Check Connections: • All boxes connected Up AND Down? • Unconnected = something missing, extra, or in wrong place • Check Language: • Unique to each level? • Check for Means-Ends Relationships • Confusions with Membership? (similar function in different part of system or exact same function?) • Confusions with Part-Whole? (belong to same subsystem with given function or serve same function themselves)

  22. Means-End Links:Some Counter-Examples Pump Valves Mass Source 1 PA PB VA1,VA2,VB1,VB2 Water Water Input 1 Input 2 Water Input 1 Water Input 1 PA VA VA1 VA2 PA VA VA1 VB1

  23. Pump Flow A Valve Flow A Valve Flow A1 Pump Flow B Valve Flow B Valve Flow B1 Pump A Valve A Valve A1 Pump B Valve B Valve B1 Part-Whole vs. Means-Ends Subsystem Components Mass Source 1 AF GF Water Input A1 Water Input B1 PFunc

  24. Information Requirements • Convert AH into a list of variables • Extract level-by-level • Start at top with Functional Purpose

  25. Functional Purpose • Measures of System Performance • Can also be measures of • Safety • Environmental Impact • Profitability ($) • Efficiency (%)

  26. Abstract Function • Measures of: • Mass • Energy • Momentum • Force • Power • Torque • Information • (Rates of) Input, (Rates of) Output, Storage

  27. Generalized Function • Temperature • Pressure • Volume • Velocity • Acceleration • Other process measures …

  28. Physical Function • Level • % open or closed Consider settings and possible states …

  29. Physical Form • Colour • Shape • Size • Length, width, depth • Location

  30. Information Availability • For each variable, determine if it is: • Currently Available • Directly sensed? • Calculated from sensor data? • Currently Unavailable • Can be sensed? • Can be calculated from sensor data? (If so, will sensor be added?) • Cannot be sensed or calculated? (May be possible in future)

  31. Information Availability Table • Currently sensed • Currently calculated • Will be calculated – requirements? • Will be sensed • Will not be sensed/calculated – solution?

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