Riistvar

Riistvar is a term used in resource-centered modeling to denote a variable that encodes the availability or abundance of a resource at a given time and location. It is typically treated as a state variable within dynamical models, capturing how resource levels change due to supply, consumption, renewal, or external shocks.

The term is a coined designation used in studies that combine resource management with mathematical modeling; the word is formed from roots that connote "resource" and "variable" in several European language families.

Characteristics of riistvar include that it can be measured or latent, continuous or discrete, and nonnegative. It typically interacts with other model variables such as growth rates, demand, or control inputs. In stochastic formulations, riistvar may follow a specified probabilistic process.

Applications span ecology, economics, and engineering. In ecology, riistvar represents prey or habitat resources that influence predator dynamics. In inventory theory or operations research, riistvar can denote stock levels of a physical resource or commodity. In energy and environmental modeling, it may represent fuel, biomass, or other inputs to production.

A simple continuous-time example uses dR/dt = s - c(R) - l(R), where R is riistvar, s is supply, c is consumption, and l is losses. A discrete-time version may be R_{t+1} = max(0, R_t + s_t - d_t).

See also: State variable; Resource management; Ecological modeling; Inventory theory; Dynamic systems. References: For general background, see standard texts on dynamic modeling and resource economics.