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Absolutely. From RFC2119:

> MUST This word, or the terms "REQUIRED" or "SHALL", mean that the definition is an absolute requirement of the specification.

>SHOULD This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.

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Thank you for posting this. At first, I thought your reply was an attempt at sarcasm—but on searching, I found the relevant RFC. Just shows that even after 30+ years of programming, there is so much that I don't know.

The British Highway Code uses similar terminology. Breaking a “must” rule is a punishable offence, where “should” rules are just for advice.

This is a common standard in aerospace requirements documents.

Join the world of needing to make the FAA happy and your vocabulary will change to incorporate shall, will, must, and others in a more discerning manner.

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