Common behavior

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• unset
  If unset, the variable is defined but does not have any active value and is invisible during the installation process.
• set
  If set, the variable has an active value, which can be still changed during panel changes depending on changing variable conditions.
• frozen 
  If frozen, the variable's value will be is not changed during the refresh . process on panel changes.

Precedence rules during refreshing

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In addition, if the user goes back through the panel sequence by pressing Previous, they must reach the first panel containing the variable before it will be unfrozen.

In this way, the variables can be reset to the proper values based on new conditions when the user navigates backward and forward multiple times and inputs new choices.

Global precedence for dynamic variable assignments

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1. User input field (for instance on UserInputPanel, InstallPanel): A valid user input is assigned as a variable value and freezes the variable from further changes during refreshing.
   Note: Each panel can access an API for registering variable names it affects or override when being active. Freezing is not just limited to the UserInputPanel.
2. Refresh: try to get the last valid value in order of the definitions taking the conditions into account
3. Refresh: try to find a default value from the <variables> section
4. Refresh: unset if the variable value cannot be assigned due to no variable condition evaluating to trueto true and the unset  attribute is not set to false for that certain variable definition.