RFC 2119
RFC において要請の程度を示すために用いるキーワード
- MUST：しなければならない
- MUST NOT：してはならない
- REQUIRED：要求されている
- SHALL：することになる
- SHALL NOT：することはない
- SHOULD：する必要がある
- SHOULD NOT：しないほうがよい
- RECOMMENDED：推奨される
- MAY：してもよい
- OPTIONAL：選択できる
参考：
Key words for use in RFCs to Indicate Requirement Levels 翻訳 | IPA
RFC 2119 – Key words for use in RFCs to Indicate Requirement Levels 日本語訳 | Mendoxi
RFC とは
RFC とは IETF (Internet Engineering Task Force) が公開している技術仕様に関する文書。”Request for Comments” (コメント募集) を意味する。
A critical point was how we wrote the RFC and the reason they’re called Requests For Comments. I stayed up all night trying to get the wording right to initiate this series of notes. I was most concerned that we not tread on someone’s toes, someone assigned officially to oversee these things. So I used wording such as “these are unofficial and they are just to stimulate conversation, and anybody is able to write down anything, and they have no status.” There was also an issue as to whether these were formal publications, and so we said they were not.
参考：
RFC は、なぜ「意見募集」という名前だったのか？ | Geek なぺーじ
Request for Comments – Wikipedia
Oral history interview with Stephen Crocker | UDC (conservancy.umn.edu)