REPLY Meaning of Stock/Level (SD6922)

[SDMAIL Alan McLucas]

Posted by  "Alan McLucas" <A.McLucas at adfa.edu.au>

George,

Thank you. We can always rely on you for your sage comments. 
Thank you for your examples.  
I have been deliberately playing "devil's advocate" with the way I have
sought to elicit comments about this topic.
>From a conceptualization viewpoint I agree that representing soft
variables as stocks is a legitimate approach.  However, representing the
growth and decay in a soft variable by using stock-and-flow diagrams to
conceptualize is not the same as claiming that such a model is strictly
valid.  If the purpose of the model is to hypothesize about how changes
in the soft variable occur, so that some form of intervention might be
designed, then this is a legitimate approach.  
However, I am still concerned that models appear from time-to-time that
clearly rely on the stock-and-flow representation of the behaviour of
soft variables satisfying some basic "truth criterion", at least in the
minds of the modeller.  Sorry, I am not at all convinced that this is
either legitimate or appropriate.
Regards,
Alan   

Dr Alan McLucas
Posted by  "Alan McLucas" <A.McLucas at adfa.edu.au>
posting date  Mon, 14 Apr 2008 08:20:16 +1000