• Homework #2 is due on Monday at 11:59 pm
• Please “read” Chapter 4: Implementing a First Agent-Based Model

Discuss: What are the components of a model?

Answer:

• Objects (nouns)
• Processes or relationships (verbs)
• Simplified, abstract/concrete (adjectives)
• Function (use case) - Not strictly necessary for the definition of a model. This answers the “Why model?” question.

Definition: A model is a simplified, abstract (or concrete) representation of objects and their relationships and/or processes in the real world.

Exercise 1: One famous example of how different models must be used to solve different problems in the same system is grocery store checkout queues.

1. Who is asking the question and for whom will the model affect? (stakeholders)
2. Why are the stakeholders wanting to model the situation? (model function)
3. What are the relevant objects and processes?
4. How should it be modeled? (model type)

1. Who is asking the question and for whom will the model affect? (stakeholders)
2. Why are the stakeholders wanting to model the situation? (model function)
3. What are the relevant objects and processes?
4. How should it be modeled? (model type)

Customer: If you are a customer deciding which queue to enter, how would you model the problem?

1. Who is asking the question and for whom will the model affect? (stakeholders)
2. Why are the stakeholders wanting to model the situation? (model function)
3. What are the relevant objects and processes?
4. How should it be modeled? (model type)

Manager: If you were a store manager deciding how to operate the queues for the next hour or so, what questions would your model address and what would it look like?

1. Who is asking the question and for whom will the model affect? (stakeholders)
2. Why are the stakeholders wanting to model the situation? (model function)
3. What are the relevant objects and processes?
4. How should it be modeled? (model type)

Designer: If you were a store designer and the question is how to design the checkout area so that 100 customers can check out per hour with the fewest employees, what things would you model?

“ODD” = “Overview, Design concepts, and Details”

Why ODD?

• Useful for describing ABMs (model protocol; standardization)
• Useful for understanding ABMs (multiple model representations)
• Useful for replicating ABMs (model reproducibility)
• Useful for formulating ABMs (modeling roadmap; guides thinking)

“ODD” = “Overview, Design concepts, and Details”

• Be able to name the benefits of using a “Materials and Methods” protocol (e.g. ODD) for reporting and organizing the steps of agent-based model design and analysis.
  • Describing
  • Understanding
  • Replicating
  • Formulating

DURF

• Develop a firm understanding of the “Overview” and “Details” elements of ODD.

• Develop an introductory understanding of the “Design concepts” element of ODD.

• Understand, from its ODD description, the model we will program and use in chapters 4 and 5.

Virtual Corridors of Butterflies

Purpose: Explore questions about virtual corridors. Under what conditions do the interactions of butterfly hilltopping behavior and landscape topography lead to the emergence of virtual corridors? How does this variability in the butterflies' tendency to move uphill affect the emergence of virtual corridors?

Question: What are the explanatory variables and processes and what is the system output we are interested in?

Entities, state variables, and scales

• Entities
• Agents: Butterflies
• Patches: Land
• State variables
• Butterflies: Patch coordinates (discrete)
• Patches: Elevation
• Scales
• Space: 150 x 150 grid; each grid is 25 x 25 \( m^2 \)
• Time: 1000 time steps; 1 step=time to move 1 patch

Process Overview and Scheduling There is only one process in the model: movement of the butterflies. On each time step, each butterfly moves once. The order in which the butterflies execute this action is unimportant because there are no interactions among the butterflies.