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Section 8 identifies sources of data to use in the SRM analysis. 

Once the system elements are listed, a careful review of the NAS change description should be conducted. A bounded system limits the analysis to the components necessary to adequately assess the safety risk associated with the NAS change, system, and/or operation. When there is doubt about whether to include a specific element in the analysis, it is preferable to include that item, even though it might prove irrelevant during the hazard identification phase. 

## 3.3.3.2 5M Model Method 

The 5M Model can be used to capture the information needed to describe the system and aid in hazard identification. The 5M Model uses a Venn diagram to depict the interrelationships among its five elements, as seen in Figure 3.5. To adequately bound and describe a system, it is important to understand the relationships between the elements of the 5M Model. 

The 5M Model illustrates five integrated elements that are present in any system: 

• Mission:  The clearly defined and detailed purpose of the NAS change proposal or system/operation being assessed 

• (hu)Man/Person:  The human operators, maintainers, and affected stakeholders 

• Machine:  The equipment used in the system, including hardware, firmware, software, human-to-system interfaces, system-to-system interfaces, and avionics 

• Management:  The procedures and policies that govern the system’s behavior 

• Media:  The environment in which the system is operated and maintained 

<img src='content_image/580333.jpg'>

The 5M Model and similar techniques are used to deconstruct the proposed NAS change in order to distinguish elements that are part of or affected by the proposed NAS change. These elements later help to identify sources, causes, hazards, and current and proposed risk mitigation strategies. 

