* 定義

[6] 
> A name space is the set of valid names for a particular item, or
the syntactic rules for generating these valid names. 

;; [CITE@en[RFC 3536 - Terminology Used in Internationalization in the IETF]] ([TIME[2011-01-29 02:14:52 +09:00]] 版) <http://tools.ietf.org/html/rfc3536#section-6>