A quantitative narrative on movement, disease and patch exploitation in nesting agent groups

Wayne M. Getz; Richard Salter; Krti Tallam

Simulations are built out of objects, called Components. Among the component types are Primitive Components, Simulators, Displays, and Controls. The primitive components consist of Stocks, Variables, Sequences, Flows, and Terms. Stocks, Variables and Sequences are used to represent the state of a running simulation. The Stock component may be attached to one or more Flows. Each Flow specifies some change in the current value of the Stock. A Variable is similar, only it is not attached to any Flow; rather its change is determined by a derivative contained in the Prime field. Sequences are similar to variables, except that they are discrete, and change is indicated by a Next field, directly determining the value of the sequence in the next time interval. Flows and Terms both have Exp fields containing their expressions. As mentioned above, Flows affect the value on the Stocks to which they are attached. A Term is used to compute a value using current State values (in Stella, what Numerus Model Builder calls a Term is referred to as a Converter.)