# A Review of Supply Chain Resilience: A Network Modeling Perspective
## 2 Overview of Supply Chain Resilience Development  
### Fundamental Concept of Resilience  
#### 2.1.1 The Concept and Origin of Resilience  
In today's interconnected world, different systems can interact and connect to generate functions that are unattainable by individual systems alone. This phenomenon is known as emergence, and systems possessing this characteristic are called Systems of Systems (SoS) [4] or multi-system integrations. SoS is widely applied across various domains, encompassing infrastructure such as urban underground pipelines and power grids, networked military organizations, and supply chain systems of large enterprises or e-commerce platforms [5]. In multi-system integrations, the interconnectivity between subsystems is tighter, but the complexity and uncertainty of such systems pose potential threats that can lead to subsystem failures, consequently degrading the performance of the entire integrated system. Maintaining the regular operation of multi-system integrations thus presents increasingly significant challenges, and mitigating the impact of these potential threats on system performance has become ever more critical [6]. The typical approach to addressing threats or disruptions faced by systems is to design robustly integrated systems. Traditional robust design typically employs probabilistic methods to optimize system parameters, making the system less sensitive to external disturbances [7] or utilizing over-specification to reduce the likelihood of failure [8]. Moreover, redundancy strategies, such as backup systems or functions, are often implemented to prevent system failures [9]. While robust design has been widely applied, its application in multi-system integration presents certain limitations. Firstly, robust design is typically suitable for single systems. For large-scale integrated systems, over-specification and redundancy strategies can impose significant economic burdens. Secondly, due to the complex emergent behaviors of multi-system integration, the threats and uncertainties it faces are more severe, making it increasingly challenging to enhance its resistance to disruptions. Rather than merely striving to improve the disturbance resistance of multi-system integration, a more effective approach is acknowledging that performance degradation in the face of disruptions is inevitable [10]. Under such circumstances, research should focus on adapting to disruptions and improving system performance post-disturbance. Resilience, which emphasizes a system's capacity to adapt and recover from disruptions or failures, provides a promising framework. By quantifying changes in system functionality before and after disruptions, resilience is particularly well-suited for multi-system integration. Figure 1: The framework of the paper. The ecologist [PERSON] [11] was among the first researchers to propose the concept of system resilience, defining it as \"a measure of a system's ability to absorb changes and disturbances while maintaining relationships among key species and state variables.\" This concept has since been widely applied in fields such as transportation, power infrastructure, economics, and social systems. The diversity of research subjects has led to multiple definitions of resilience. For instance, the U.S. Department of Homeland Security defines resilience as the ability of assets, systems, or networks to sustain functionality or rapidly recover during terrorist attacks [12]. The American Society of Mechanical Engineers describes it as the ability of a system to continue functioning under external or internal disruptions or to recover following failure quickly [13]. The U.S. National Infrastructure Advisory Council views resilience as the capacity of infrastructure systems to anticipate, absorb, adapt to, and recover from disruptive events such as natural disasters [14]. In the field of systems engineering, resilience is often defined as the ability of a system to adapt and recover to normal operating conditions after experiencing disruptions [15].