Using Delay Elements

Delay elements simulate processes that delay continuous or discrete signals and flows. That is, their outputs lag their inputs. Therefore, like Stocks, their outputs are functions of prior values of their inputs. As a result, Delays impart inertia and memory to a system, and can internally generate dynamic behavior within a system. Without elements like Delays and Stocks, your models could respond to outside (exogenous) drivers, but could not generate any dynamics of their own internally.

Depending on the structure of your model, a Delay can lead to instability and oscillation, or it can act to filter out unwanted noise.

GoldSim provides four Delay elements:

• Information Delays are intended to represent processes such as delays in measuring or reporting variables (e.g., reporting the inventory in a warehouse, or snow pack levels), and the gradual adjustment of perceptions based on available information (e.g., sales forecasts).

• Material Delays are intended to represent delays in the physical movement (flow) of material through a system (letters though the mail system, parts on an assembly line, salmon in a river, water moving through a pipe). Material is conserved as it moves through a Material Delay. Information is not conserved in an Information Delay.

• Event Delays provide a mechanism for delaying a discrete event signal (i.e., a discrete signal that indicates that something, such as an accident or a bank deposit, has occurred). Among other things, Event Delays can be used to simulate queues.

• Discrete Change Delays provide a mechanism for delaying a discrete change signal (i.e., a discrete signal that can instantaneously change the value of a Stock element).

Information Delays and Materials Delays are used to delay continuous signals and flows.

Event Delays and Discrete Change Delays are used for representing delays in discrete signals. Use of these two elements requires an understanding of how GoldSim simulates discrete events.