Netlogo includes a stocks and flows component (system dynamics
modeler) <http://ccl.northwestern.edu/netlogo/docs/systemdynamics.html/
>. I don't believe the network of stocks and flows is reconfigurable
at runtime though it does have a basic integration with the agent-
based modeling side of Netlogo which allows for some cool
possibilities. So a stock can represent some aggregated property of a
dynamically changing agent population. And going the other direction,
the agent population can react to some changing flow or stock at the
SD level.
In addition to the dynamic nature of the interaction networks, I think
SD models differ from ABM mostly as they tend to be models of more
aggregate properties of a system whereas ABM are more micro looking at
agent interactions that give rise to macro stocks and flows. There are
nice "docking" experiments out there that look at the common results
and the advantage of each approach modeling the same system. Lotka-
Volterra (wolf/sheep), Infection models (SIR), and supply chain are
three of the most common model types I've seen.
-S
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On Aug 28, 2009, at 9:02 AM, Russ Abbott wrote:
The other day I described a framework (service-oriented agent-based
modeling) that I thought would suit the kinds of M&S I want to do.
As far as I know there isn't any literature on this sort of modeling
paradigm. But if a re-interpretation of stocks and flows modeling
can be understood in that light and if work has already been done in
that area, I want to know about it so that I don't reproduce that
effort.
-- Russ
On Fri, Aug 28, 2009 at 7:42 AM, Douglas Roberts <d...@parrot-
farm.net> wrote:
Why are you asking this? Do you want to build an ABM of a system
that models stock transactions, or write a paper about how do do so,
of just find a place for this class of simulation that fits your
worldview?
--Doug
On Fri, Aug 28, 2009 at 8:26 AM, Russ Abbott <[email protected]>
wrote:
My question was simpler than that. Is there work on stocks and flows
models in which the network structure is not static?
-- Russ
On Fri, Aug 28, 2009 at 6:59 AM, Nicholas Thompson <[email protected]
> wrote:
All,
I have tried to stay out of this discussion because I know even less
about this subject than usual, if such a thing is possible. But .....
Russ Abbott wrote:
In a service-oriented agent-based model the agents have the ability
to reconfigure themselves dynamically and perhaps even to add new
agents and new stock nodes. In a stocks and flows model, the
structure of the network static.
Which led me to wonder if there is any thing lurking in the notion
of "self-reconfiguration" here that might be making the programing
more difficult. What would be lost (or gained) if we replaced the
words "ability to reconfigure themselves" with the words "sometimes
are reconfigured". That's the thing about metaphysics: cant live
with it; cant live without it. At the risk of saying something both
controversial and incomprehensible, isnt the notion of self-
organization literally a non starter because, in control theory, the
control parameter, the measure by which the system takes stock of
its own organization, is always some part or feature of the system,
not the whole system. It's a cue.
all be best,
Nick
Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([email protected])
http://home.earthlink.net/~nickthompson/naturaldesigns/
----- Original Message -----
From: Russ Abbott
To: The Friday Morning Applied Complexity Coffee Group
Cc: Antony W. Iorio; [email protected]; [email protected]
; Lowe,Donald
Sent: 8/28/2009 5:49:40 AM
Subject: Re: [FRIAM] Agents, stocks, and flows
In a discussion with a colleague today we talked briefly about
stocks and flows networks. It struck me that a stocks and flows
model is a limited sort of service-oriented agent-based model. In a
service-oriented agent-based model, agents accept inputs and produce
outputs -- the simplest version being a supply chain. That's really
a stocks and flows model in which the agents control the flows.
Important differences are:
• In an agent-based model, the agents are assumed to be autonomous
in various ways. In a stocks and flows model the flow rates are not
autonomous. The flow rates are equations that don't have the ability
to change themselves.They are assumed to be facts about the nature
of the domain being modeled.
• In a service-oriented agent-based model the agents have the
ability to reconfigure themselves dynamically and perhaps even to
add new agents and new stock nodes. In a stocks and flows model, the
structure of the network static.
So this raises the question whether anyone knows of any work in
stocks and flows modeling that addresses stocks and flows networks
that are flexible in the ways just mentioned.
-- Russ
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FRIAM Applied Complexity Group listserv
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lectures, archives, unsubscribe, maps at http://www.friam.org
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FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org
============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org
