Parts closure in theoretical self-replication:
“Fundamental to the problem of designing self-replicating systems is the issue of closure.
In its broadest sense, this issue reduces to the following question: Does system function (e.g., factory output) equal or exceed system structure (e.g., factory components or input needs)? If the answer is negative, the system cannot independently fully replicate itself; if positive, such replication may be possible.
Consider, for example, the problem of parts closure. Imagine that the entire factory and all of its machines are broken down into their component parts. If the original factory cannot fabricate every one of these items, then parts closure does not exist and the system is not fully self-replicating .” (http://www.islandone.org/MMSG/aasm/AASM53.html#536)
“Closure engineering, in the second sense, is the closure of the parts of the supply chain such that you find that you can fully trace, implement, deploy, manage, automate the supply of energy from the local star, materials from the celestial bodies (so far this means Earth), as well as the parts, tools, processes, or machines to pull it off, for the use of a well-defined, but ambiguously defined here, community or social structure.”