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System Pillar “System of Systems (SoS)” approach

Because of the size of the Railway System, it is necessary to distinguish for the content structure between different level of details (design level). There is a hierarchy of process and system architecture levels (shown here by examples per level):



Because there are tens of thousands of requirements triggering the design process of a large process landscape/architecture that are coming up over time at any place and from any source it is highly important that the content structure simplifies the allocation of requirements. In the lifecycle of a requirement, broken down to detailed system requirements in the system requirement specification, the responsibility changes during the breakdown process.


In the same way the operational analysis on railway system level, Task level and on domain level produce different levels of details for the process description.

System LevelArea (example)Level of process details, examples (indicative)
Level 1Public TransportThe basic requirements, how railways and other transport systems shall interact concerning management connections in a station
Level 2Railway SystemHow shall customer care, ticket sales, customer information, TMS and CCS interact in general to manage a deviation (described as basic requirements)
Level 3CCS- Command and Control SystemsHow shall different actors in the production (trains, field forces, ..) be coordinated to execute a changed plan (requirements, basic process)
Level 4Vehicle Control and SupervisionWhat processes shall happen onboard in general when the movement authorisation changes (requirement, basic process)
Level 5Onboard Safety LogicWhat is the safety reaction to a change of the movement authorisation