Specification tree
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
- Assembly¹ specifications - generated by subsystem responsible contractors
- Unit specifications - generated by subsystem (or assembly) responsible contractors.
- Assembly¹ specifications - generated by subsystem responsible contractors
- Subsystem specifications - generated by system responsible prime contractor
- System (design to) specification - generated by system responsible prime contractor
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).