This was posted back somewhere in the
JT610 thread.
Reaching agreement in the presence of faults. Well worth a read on the required number of sensors to ensure redundancy for decision making in automation with faults.
M. PEASE, R, SHOSTAK, AND L. LAMPORT SRI Internationall, Menlo Park, California
ABSTRACT. The problem addressed here concerns a set of isolated processors, some unknown subset of which may be faulty, that communicate only by means of two-party messages. Each nonfaulty processor has a private value of reformation that must be communicated to each other nonfaulty processor. Nonfaulty processors always communicate honestly, whereas faulty processors may lie The problem is to devise an algorithm in which processors communicate their own values and relay values received from others that allows each nonfaulty processor to refer a value for each other processor The value referred for a nonfaulty processor must be that processor's private value, and the value inferred for a faulty one must be consistent wRh the corresponding value inferred by each other nonfanlty processor It is shown that the problem is solvable for, and only for, n ≥ 3m + 1, where m IS the number of faulty processors and n is the total number. It is also shown that if faulty processors can refuse to pass on reformation but cannot falsely relay information, the problem is solvable for arbitrary n ≥ m ≥ 0. This weaker assumption can be approximated m practice using cryptographic methods KEY WORDS AND eHRASES, agreement, authentication, consistency, distributed executive, fault avoidance, fault tolerance, synchronization, voting
Note, this is a cut and paste from an OCR .pdf, so errors may appear in the abstract, see original
Boeing know and understand this redundancy & fault tolerance problem extremely well. The fact this kludge was implemented apparently against the basic & fundamental engineering principles
and with great silence is highly concerning. There must have been substantial objections about the lack of fault tolerance from engineers who reviewed this fix. One has to wonder just how many were involved in the decision making process to implement this, and at what level.