*3.1. The System's Boundaries and Structure*

After analyzing the inherent interactions among the key risks and markets, this model determined the main variables, as well as their mutual influences and causal relationships. To describe the prominent variables and links in a structured way, the definitions and functions of the components within each market are presented in the subsequent subsections. Two bold arrows represent the interactions between the natural gas and electricity markets. Risk factors affecting each market may propagate to the coupled markets via these interactions. Different strategies can be adopted in response to the risks, including reducing demand and improving the emergency supplies [8], which can help the system to recover from risks or amplify the losses. As described below, four causal feedback loops can be easily observed.


Among the causal feedback loops, the notation "B" suggests a balancing loop that stabilizes the systems, while the notation "R" implies a reinforcing loop that amplifies the system's changes. These feedback loops foster the complex evolution of the coupled markets in the face of risks.
