Specification tree

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A specification tree shows all specifications of a technical system under development in a hierarchical order.

For a spacecraft system it has the following levels:

  • System (requirements) specification - generated by customer
    • System (design to) specification - generated by system responsible prime contractor
      • Subsystem specifications - generated by system responsible prime contractor
        • Assembly[1] specifications - generated by subsystem responsible contractors
          • Unit specifications - generated by subsystem (or assembly) responsible contractors.


  1. ^ An assembly level is defined as intermediate level when the subsystem contractor prefers to contract a group of units with complex interfaces to another contractor (for instance the operating system and subsystem application software can be an assembly of the data management subsystem).