As someone who does systems engineering, the only valid requirements include the word "shall".

stackskipton 5 hours ago | parent | next [-]

As someone else who does System Engineering, when dealing with ancient protocols, "shall" is extremely difficult barrier to get over since there is always ancient stuff out there and there might be cases not to do it, esp if it's internal communication.

"SHOULD" is basically, if you control both sides of conversation, you can decide if it's required looking at your requirements. If you are talking between systems where you don't control both sides of conversation, you should do all "SHOULD" requirements with fail back in cases where other side won't understand you. If for reason you don't do "SHOULD" requirement, reason should be a blog article that people understand.

For example, "SHOULD" requirement would be "all deployable artifacts SHOULD be packaged in OCI container". There are cases where "SHOULD" doesn't work but those are well documented.

	▲	josephg 2 hours ago \| parent [-]
		> … when dealing with ancient protocols I’m doing some work with an email company at the moment. The company has been in the email space for decades. Holy moly email is just full of stuff like this. There is an insane amount of institutional knowledge about how email actually works - not what the specs say but what email servers need to actually do to process real emails and deal with real email clients and servers. The rfcs try to keep up, but they’re missing a lot of details and all important context for why recommendations are as they are, and what you actually need to do to actually process real email you see in the wild. (And talk to the long tail of email software). This conversation makes me think about cornering some of the engineers with a microphone. It’d be great to talk through the specs with them, to capture some of that missing commentary.

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opto 5 hours ago | parent | prev | next [-]

In a completely different field, navigating ships at sea, the Collision Regulations which define how people must conduct ships at sea, they use the words "Shall" and "May" to differentiate legal requirements and what may just be best practice. "Should" intuitively means something more like "May" to me

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Arnt 5 hours ago | parent [-]

Happily, the meanings in RFCs are clearly specified, see https://www.rfc-editor.org/rfc/rfc2119.

Note "the full implications must be understood and carefully weighed before choosing a different course". Gmail and the other big hosters have full-time spam teams who spend a lot of time weighing implications, so I assume the implications of this was weighed.

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patmorgan23 4 hours ago | parent [-]

And EVERY rfc has a paragraph talking about rfc 2119 in the preamble.

	▲	prerok 4 hours ago \| parent [-]
		I guess that's why nobody reads it. /s

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sas224dbm 4 hours ago | parent | prev [-]

"shall" and "must"