A documentation scheme has been described which is equally appropriate for hardware and software. This scheme is useful for conceptually formulating, designing, developing, manufacturing, installing, testing, and using the system. This documentation system evolves with the system that it describes. This scheme further unambiguously describes all aspects of the system in an easily update form and in a way such that any specific piece of information appears in only one place. A secondary benefit of structuring a system in the manner described is that if a design change is dictated at any point during the life cycle of the system, the extent of the impact of that change can easily be evaluated. For example, if a design change is indicated for the unit lube oil system and an examination of the interfaces of the specific system indicates that they are not affected by the change, then the design change can be implemented without notifying anyone because that design change is not going to have any influence on any other part of the system. Because that design change is not going to have any influence on any other part of the system. Because the interface flows are not changed, the remainder of the system is unaware that a change has occurred. If the proposed design change does result in a change at one or more of the interface flows of the unit lube oil system, then one goes to the interfaces of the unit engine system (the (the immediately superior system level to the unit lube oil system) and determines if those interface flows are altered by the design change. If not, then only the sibling elements to the unit lube oil system need to be examined for the effects of the proposed design change. If the unit engine system interface flows are changed, then one goes to its superior element (the engine system) and examines its interface flows, etc.