Based on RFC 2119: “Key words for use in RFCs to Indicate Requirement Levels”:
... 3. 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. ...
gem install rfc_specIf you want to hack on rfc_spec, clone it from GitHub:
git clone git://github.com/seattlerb/rfc_spec