A specification tree shows all

specifications A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard. There are different types of technical or engineering specificati ...

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 **** AssemblyAn 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 An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...

and subsystem

application software Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a ...

can be an assembly of the data management subsystem). specifications - generated by subsystem responsible contractors ***** Unit specifications - generated by subsystem (or assembly) responsible contractors.

References

Product development Systems engineering {{tech-stub