[1] URN 亜空間 urn:x-suika-fam-cx:msgpm は、 manakai が内部で使用する名前のためのものですが、 もちろんそれ以外でも使用することができます。 主として 822 的メッセージの構造の部分を識別するのに使うことができます。

[2]

[3] field-names are case-insensitive. Lowercase is the canonical form and is recommended. Resolution 2005-05-19

[4] Some header field might be encoded in multiple forms of URIs.

For example, an RFC 2822 header field List-ID is representable as both <urn:x-suika-fam-cx:msgpm:header:mail:rfc822:list-id> and <urn:x-suika-fam-cx:msgpm:header:mail:list:id>. In this case, the urn:x-suika-fam-cx:msgpm:header:mail:rfc822:list is deprecated and the later URI should be used.

Another example. An RFC 2822 message header might have a header field of name Content-Language. URI reference of it might be <urn:x-suika-fam-cx:msgpm:header:mail:rfc822:content-language> or <urn:x-suika-fam-cx:msgpm:header:mime:content-language>. Both URIs are valid and you can use which is appropriate (or useful).

Resolution 2005-05-19

[6] Use of percent-encoding: As in RFC 3986, any unreserved octets may safely be percent-encoded and decoded, while the decoded form (i.e. using the unreserved character itself is recommended). If a field-name contains non-unreserved character, then the character must be percent-encoded. Resolution 2005-05-19

[5] Using these URI references as XML vocabulary. These URI references might be encoded as QNames and be part of XML document type. On such an information item, the URI reference minus field-name is namespace name and the field-name, with all latin letters in lowercase, is local name. See 全文検索用中間形式 (>>6) for example.

NOTE: If a field-name has one or more characters that is inappropriate as in an XML Name, then the URI reference is impossible to represent in the XML form.

Resolution 2005-05-19

[7] Equivalence: In addition to the equivalence algorithms defined for urn:x-suika-fam-cx: URI references, there is an equivalence level <http://suika.fam.cx/~wakaba/archive/2005/5/equiv-header-field-name> Resolution 2005-05-19.

• If two URI references start with urn:x-suika-fam-cx:msgpm:header: (for urn and x-suika-fam-cx any case-combinations are allowed),
  1. Converts all capital Basic Latin letters (LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) to the lowercase.
  2. Compares two URI references in character-by-character basis.
• If one of URI references does not start with urn:x-suika-fam-cx:msgpm:header:, this algorithm does not define the equivalence.
  • NOTE: Any other algorithm combined with this algorithm may or may not define such equivalence.
• Note that unreserved characters are always percent-encodable. It might be required to decode before the test.