[3] 
>
:"SHOULD":This word or the adjective "RECOMMENDED" means that there
may exist valid reasons in particular circumstances to
ignore this item, but the full implications should be
understood and the case carefully weighed before choosing
a different course.

;; [CITE@en[RFC 1123 - Requirements for Internet Hosts - Application and Support]] ([TIME[2010-07-22 04:07:59 +09:00]] 版) <http://tools.ietf.org/html/rfc1123#page-11>

* メモ

[1]
[CITE@en[XML Query (XQuery) Requirements]] ([CODE[2007-03-17 06:39:09 +09:00]] 版) <http://www.w3.org/TR/2007/NOTE-xquery-requirements-20070323/#terminology-should>

[2]
[CITE@en[XML Query (XQuery) 1.1 Requirements]] ([TIME[2007-03-16 09:42:40 +09:00]] 版) <http://www.w3.org/TR/2007/WD-xquery-11-requirements-20070323/#terminology-should>


[4] [CITE@en[RFC 4835 - Cryptographic Algorithm Implementation Requirements for Encapsulating Security Payload (ESP) and Authentication Header (AH)]]
( ([TIME[2011-02-03 22:05:20 +09:00]] 版))
<http://tools.ietf.org/html/rfc4835#page-4>