Using exogenous quantities in qualitative models about environmental sustainability

Representing the impact of external factors on the behaviour of a system is a challenge for modellers, particularly when these factors are dynamic and may change during the simulation. This article presents mechanisms implemented in the qualitative reasoning engine Garp3 for modelling quantities that exhibit exogenously defined behaviours. Exogenous quantities are those that influence the system but are not influenced by quantities represented in the system. Seven types of mechanisms for handling exogenous quantities are implemented: “constant”, “generate all values”, “increasing”, “decreasing”, “steady”, “sinusoidal”, and “random”. Examples drawn from models of environmental sustainability (related to Millennium Development Goal 7) are used to illustrate the functioning of these primitives. Individually or combined, the mechanisms provide many options for modellers to represent cycles, oscillations, and regions of local stability.

• Type: Journal
• Year: 2007
• Where: AICOM
• Authors: Bert Bredeweg, Paulo Salles, Tim Nuttle
• Keywords: AICOM 2007, Exogenous Quantities, External Factors, Qualitative Reasoning Engine