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