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Problems and Frames IV

Problems and Frames IV. Heuristics. Heuristics?. Serving or helping to find out or discover; Guidelines; But connotations of trial and error. Heuristics. Principal steps: Identify the core problem Identify the ancillary problems Standard decompositions of sub problems

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Problems and Frames IV

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  1. Problems and FramesIV Heuristics

  2. Heuristics? • Serving or helping to find out or discover; • Guidelines; • But connotations of trial and error.

  3. Heuristics • Principal steps: • Identify the core problem • Identify the ancillary problems • Standard decompositions of sub problems • Identify concerns and difficulties

  4. More heuristics • Different tempi • More than two moods • Complex domain or requirement • Modelling the user

  5. Different tempi • When one part of your problem is in a slow tempo and one in a fast tempo, treat them as different sub problems. • Look at Tennis Court Lights handout • What are the different tempi?

  6. More than two moods • Every frame has at least 1 description (of domain properties) in the indicative mood • And at least two (req. and spec.) in the optative mood. • Sometimes you need 3 moods which indicates presence of at least two subproblems • Look at Air Traffic Control

  7. Complex domain or environment • In each basic frame a clear expectation of relative complexities of the domains and requirement complexity • Req. Beh. Frame: controlled domain may be complex, but you expect the requirement to be satisfiable by simple control law. • Commanded Beh. Frame: Controlled domain complex, but controller simple.

  8. Continued • Info. Display Frame: RW complex, display domain quite simple. Req. = simple relationship between req and specification phenomena of RW • Workpieces: w/pieces may be complex, user domain simple • Transformation: inputs & outputs of roughly equal complexity. I/O relation satisfiable by traversal of both domains

  9. Continued • An unusually complex domain indicates a possible further decomposition • Package router: core problem was Required Behaviour. • Complexity = destinations not available to sensors, so introduce a model domain = new subproblem

  10. Modelling user • In workpieces frame, user domain is unstructured stream of commands • Where user domain is of interest for its own sake, this indicates a subproblem • If we need to know who edited a workpiece, we need a model of each user to record individual editing activities. This is a separate problem

  11. Exercises • What are the different tempi in the Home Heating Control problem? • What are the moods in the Package Router problem? • What are the subproblems in the University Administration system?

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