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Deciphering the code: understanding the output structure
Woodstock outputs
Deciphering the code: understanding the output structure
Applies to: Spatial Woodstock all versions
Date: September 15, 2007
Outputs are the key to using Spatial Woodstock models. You use outputs to declare objective functions and constraints (that is, to describe the characteristics of the desired solution) and for reporting and analysis. Without them, the model would run but would be practically useless. That being said, the output structure is one that can cause some confusion. The purpose of this tip is to describe the output structure and how it determines the underlying output calculation.
In technical terms, outputs are time-indexed arrays of numbers whose values are calculated by summing the product of an area and a value of interest on a development-type-class-by-development-type-class basis for each period in the model. So any output calculation requires an area and a value to sum (i.e., a yield, age or area), both of which are associated with development types.
The generalized, basic output structure is as follows (excluding optional modifiers):
*OUTPUT OutputCodeName Description
*SOURCE DevelopmentTypeMask AreaLookup ValueToSum
It is the AreaLookup component that is of particular interest as it determines the area values used in the output calculation.
Basic outputs come in two flavors: [1] inventory outputs and [2] action outputs. Inventory outputs obtain areas from the internal inventory of area by development type and age and have the _INVENT keyword in place of AreaLookup (the Areas section represents the initial inven¬tory); action outputs direct the model to obtain areas from the Schedule section and have an action code in place of AreaLookup.
Examples (assume that the model contains two themes).
Inventory output
*OUTPUT oStandingVolume Total standing inventory
*SOURCE ? ? _INVENT yTotalVolume
This inventory output directs the model to, in each planning period, take each existing develop¬ment type class, lookup its area in the inventory of areas and multiply it by the value of the yTotalVolume yield table, and sum the result for all development types classes processed.
Action output
*OUTPUT oHarvestVolume Total volume harvested
*SOURCE ? ? aHarvest yTotalVolume
This action output directs the model to, in each planning period, take each development type class scheduled for a harvest, lookup the area harvested in the Schedule section and multiply it by the value of the yTotalVolume yield table, and sum the result for all development type classes processed.
There are optional modifiers (e.g., @AGE, @YLD, etc.) that you can use in output declarations to refine the calculation even further, or to sum areas or ages, but the basic output structure will always include the three components described here, that is a development type mask, the section from which to obtain area and a value to sum.
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