GCDC Status Report April 12 A Model Focus

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GCDC - Status Report April 12A Model Focus

• Scope Overview
• Modelling Issues
• Mental Model Hypotheses versus Model,
• Scope Creap, ...
• Representation Linking variables, ...
• Technical Detailed calculus,
• Behavior Relevance of details,
• Old Issues
• Understanding resource Dynamics contact with
  NOAA

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Scope Overview (CL) -1
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Scope Overview (CL) - 2
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Scope Overview (CL) - 3
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Model Issues A changing mental model

• Approach was more or less
• Build, understand grow (dont understand) and
  collapse simplify
• Tradeoffs of fitting
• previous built up understanding of reality
• Difference between rational of D-fishermen versus
  W (attractiveness and choice for white fish)
• Hypothesis versus Model
• hard to keep the client really up-to-date

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Model Issues Scope and Details

• Scope Creap
• Sometimes good (better understanding),
  butdangerous
• Detail
• want little, but grows easily
• When you dive into details, life is not that
  simple
• simple case expected attractiveness
• Many, many intermediate beavioral delays
• and more to come e.g. days at sea

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Model Issues - Representation

• Linking variables
• tradeoff between many links and the dead bull
  again
• Views
• (breaking up)
• For who?
• Dynamic Hypothesis as backup, but representation
  changes
• Colorcodes
• Table functions,..loopvariables,..

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Model Issues - Technical

• Longwinded Calculus
• Uglyno feedbackbut relevant!?
• Same principle as before want to make relations
  explicit
• Example LAB activity Calculation
• Time conversions
• some inherent in model assumptions, some
  constraining simplicity
• Organization
• Filing versions and runs
• All in new directory, with version coding
• New name when large change
• Include date in version

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Model Issues - Behavior

• Understanding all behavior versus Complexity
• Starting in equilibrium after a parameter change
• List of modifiable parameters
• Details Cyclic behavior relevant or not
• (in this case yes!)
• Adding Common Sense table Functions
• (e.g. demand elasticity)
• Und jetzttesting the hypotheses

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Dynamic Hypothesis

• Potential Factory output The potential factory
  output should be determined by the availability
  of fish stock. Pushing the system based on the
  attractiveness will finally limit the factory
  output.

Potential factory output
t
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Some Results