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 and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

and subsystem

application software Application software is any computer program that is intended for end-user use not operating, administering or programming the computer. An application (app, application program, software application) is any program that can be categorized as ...

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