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## 4.2.7 Other Documentation 

Documentation relating to existing design, tests, field performance, NAS operations research, and detailed support (perhaps including recent SRM documents or portfolio SRM documents) may already exist for the replacement, removal, or reconfiguration of existing NAS systems; these may apply substantially to the new proposed action. The PO should consider conducting an audit for applicable and reusable baseline documents and SRM documents that can form a sound basis for legacy architecture, requirements, design, performance, and known NAS constraints. 

## 5 OSA Development Process 

## 5.1 OSED Development Process 

The OSED captures elements that comprise a CNS/ATM system (e.g., aircraft equipage, air traffic service provider technical systems, communication service provider systems, and procedural requirements), and it includes the operational performance expectations, functions, and selected technologies of the CNS/ATM system. The OSED facilitates the formulation of technical and procedural requirements based on operational expectations and needs. 

Figure C.2 gives a logical overview of the steps required to conduct an OSED. Some of the steps may overlap or be iterative in nature. 

<img src='content_image/513376.jpg'>

The required tasks for preparing an OSED are described in Section 5.1.1 through Section 5.1.4. 

## 5.1.1 Define the Boundaries 

Define the boundaries of the solution under consideration, including anticipated interfaces, a technology’s independent layers, and common services among NAS systems and sub-systems (both internal and external). Determine, separate, and document which elements of the solution to describe and analyze for hazard identification. Identify shared resources (if any) for which independent SRM was already performed. 

## 5.1.2 Describe the Physical and Functional Characteristics of the Solution’s Concept 

Using models such as those described in the SMS Manual (e.g., the 5M Model), describe: 

• The concept’s state by including physical and functional characteristics, 

• The environment’s physical and functional characteristics, 

• Air traffic services to be provided, 

