Re: Simulating Individual Behavior

[cgl]

Paul Fishwick wrote:

>A key problem with IBM is not that it is necessarily
>computationally prohibitive, but that not enough data are
>available to calibrate the model...

 Paul - why is data calibration more of a problem for IBM
models than for other modelling technologies? What sorts
of problem domains are you particularly concerned about?

 I can allow as how it would be difficult to calibrate
an IBM model of a forest precisely so that each tree-agent
is parameterized via data taken from its respective
real-tree in the forest. Yet, all modelling technologies
make do with some degree of approximation. A reservoir-flow
model of tree-species interaction in a forest would simply
treat all of the trees of each species as "one big tree" 
of that species with respect to some data (such as  concentration, 
nutrient uptake, waste-production, and etc.) while ignoring
other data (such as spatial distribution, variety within the 
species, and etc.) This will be justified for certain questions 
about forest dynamics, but not for others, and might make more 
sense for some problem domains than for others. 

Thus, there is data and there is data. All modeling technologies
must pick and choose among the data, and one always has to 
focus on some reasonable subset of data.  You seem to 
be suggesting that this is fundamentally more of a problem
for IBM models than for other modelling technologies
- can you elaborate?

  ...and, please!, it almost *hurts* to use the acronym IBM!
could we use "ABM" for Agent-Based Models? I think it fits
better anyway, as an agent in this class of models is not 
always an "individual" in the common sense of that term....
I know the term has some historical precedent for models
in this class, but the acronym IBM induces a certain amount 
of, shall we say, cognitive dissonance, no? (not that the 
acronym "ABM" itself is inviolate with respect to prior 
cognitive content....but, still!.....)


Chris Langton


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