Entities, State variables, and Scales

a. Entities: These are the parts or components represented in the simulation. They can be individuals, objects, organizations, or other relevant elements in the modeled system.  Identifying and defining these entities is important as they form the building blocks for simulating interactions and behaviors in the system. Distinct objects/actors, agents, spatial unit such as grid, polygon, collectives, objects and environment, landscape consists of grid cell.

b. Variables: Variables represent the characteristics or attributes associated with the entities in the model. They describe the current state or condition of each entity.  Variables capture the dynamic nature of entities and their interactions in the simulation.

c. Scales: Scales refer to the levels at which the model operates, such as spatial, temporal, or organizational levels. Spatial scales determine the size and resolution of the simulated environment.  Temporal scales determine the time increments in the simulation, like seconds, hours, or days. Organizational scales involve hierarchical or nested levels within the model, such as individual entities, groups, or systems.

Extent and Granularity in Scales

- extent: overall size or scope of the model in both space and time

- granularity: level of detail at which model's space and time represented

1. Entities

• Entities are the components of the simulation: agents, environments, and time
• In the ITC Simulation model, there are 3 types of agents: leavers, followers, and officers (differentiation based on the goals)
• There are also several environments: the walls, the walkable space, the distance to the nearest exit, the distance to the main exit, and the network representing the center lines of the corridors and, of course, the exits. 

2. State Variables

Attributes of each kind of entity. Example : age, color, size, shape, etc.

State Variables for the ITC Simulation :

• Agents: status (not evacuating yet, evacuating, evacuated)
• As a rule of thumb, state variables are variables that cannot be calculated or deduced from other variable

3.  Space and time

Model runing in time, how large the area eing simulated, how small is the single unit.

In the model of immigrant housing model (previous year's exam)

• Spatial Extent: the entire island of Montreal and its residential areas
• Temporal Extent: 5 years
• Spatial Granularity: Might be each residential area or the grid raster
• Temporal Graniularity: likely on year, as decisions and updates are made manually