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Years under the bridge... we're on Drupal 7.1! :-)

It has been a long time coming but we have taken the plunge and updated the Local Food Economy Game website to Drupal 7.1. The security aspect of moving from 5.x to the latest was a prime factor. This project originally started in the Drupal 4.7 era! We transitioned to the 5.x platform during the project's active time. I did a 6.x migration that languished at the sandbox/development stage while other things took priority. Then I resurfaced this project to address the security aspect as well as scratch the itch to begin exploring the 7.x platform.

Use Case Observations from Grinnell Farmers' Market

From my visit to the Grinnell farmers' market on August 11, 2006, I designed both a template for interactions between vendors and customers, and a set of use cases depicting these interactions.

Buyer and Seller Interaction at Farmers' Markets

I have been trying to figure out the Metamodel presented by Jim yesterday on this website. I have tried to work through a simple model of an interaction between a buyer and seller at a farmers' market; it is shown below in the attached document. I am certain that this is not precisely how the interaction would be represented in our ABM program; any thoughts on how it should be altered? I want to make sure I have a simple interaction down before I move on to modeling larger environments, such as the entire farmers' market.


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Forecasting Consumer Price Indexes for Food

Located here is an article entitled "Forecasting Consumer Price Indexes for Food: A Demand Model Approach," by Kuo S. Huang. Huang uses an inverse demand function to assess the change in quantity demanded for a variety of goods (including beef, eggs, fruits, vegetables, cereal) based on a one percent change in price of that good. Huang presents a chart that shows, for example, that a one percent increase in the price of poultry would result in a .84 percent decrease in the quantity demanded of poultry. He also gives figures for cross elasticity of demand: A one percent increase in the price of red meat, for example, .91 percent decrease in the quantity demanded of beef.

More on NetLogo

Having downloaded NetLogo and played around with it for a while, I am unsure whether it will meet the needs of our modeling project.

  • NetLogo is particularly aimed at modeling systems as they adapt over time. Agents in NetLogo continuously respond to each other's decisions, resulting in an ever-changing environment. To a great extent, we are interested in modeling a system that will develop over time: at a farmers' market, for example, a seller makes a decision (setting up a vendor station), a buyer makes a decision motivated by the seller's decision (walking over to the vendor station), then another decision (whether or not to buy from the this particular vendor), etc. For these types of interactions, it is crucial to have a simulation program that effectively displays change over time in the system, showing how decisions by each agent impacts each following decision by other agents.

Directory of agent-based modeling links

Located here is a directory of links to applications of agent-based modeling, arranged by subject area. Of greatest importance to us is the economics section, which includes such projects as "artificial life simulation of the textile/apparel market," and "agent based simulation of the hotelling game." The page is put together by Craig Reynolds.

A simple introduction to agent-based modeling

For those who are unfamiliar with agent-based modeling (ABM), here is an easy-to-understand introduction to the subject. It is a list of answers to frequently asked questions about ABM, entitled "Agent-based modeling of complex, adaptive systems." It explains how agent-based modeling allows these systems to be modeled, and why modeling is a useful tool for understanding these systems.

Some articles on agent-based simulation

Just to update on some of the work I've been doing, here and here are links to a couple articles I've read about agent-based simulation that I did not find worthy of individual write-ups as they are not particularly useful to our project. The first article, by Robert Axelrod, presents a walk-through for those who plan to begin an agent-based simulation project, but does not really advance any new ideas for us.

The World is Flat

Now that I have finished "Field that Dream" and "Fields of Plenty," I will continue with my reading of Thomas Friedman's "The World is Flat." As I make connections between the book and LFE and/or Sohodojo content, my thoughts will go up here.

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