Describing and Formulating ABMs: The ODD Protocol

• Reminder: Homework #4 due this Wednesday!
• Homework #5 will be up on Blackboard this evening
• Let's take a look at the schedule shall we?

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”

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?

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