#?SuikaWiki/0.9 page-icon="メイル" import="メッセージ訳語集,その他の訳語集,RFC訳語集"

[SEE[ [CODE[Message-Context:]] ]]

'''Message Context for Internet Mail [INS[__&&Internet&&____&&mail&&__の__&&message&&__文脈]]'''
- Network Working Group                                          
- Request for Comments: 3458                            
- Category: Standards Track 
- E. Burger
- SnowShore Networks              
- E. Candell
- Comverse
- C. Eliot
- Microsoft Corporation
- G. Klyne
- Nine by Nine
- January 2003


* Status of this Memo

> This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements.  Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol.  Distribution of this memo is unlimited.


* Copyright Notice

> Copyright (C) The Internet Society (2003).  All Rights Reserved.


* Abstract

[PRE[
   This memo describes a new RFC 2822 message header, "Message-Context".
   This header provides information about the context and presentation
   characteristics of a message.
]PRE]

[PRE[
   A receiving user agent (UA) may use this information as a hint to
   optimally present the message.
*Table of Contents
]PRE]

[PRE[
   1. Introduction....................................................2
   2. Conventions used in this document...............................3
   3. Motivation......................................................3
   4. Functional Requirements.........................................5
   5. Determining the Message Context.................................6
   6. Message-Context Reference Field.................................7
     6.1. Message-Context Syntax......................................7
     6.2. message-context-class Syntax................................7
       6.2.1. voice-message...........................................8
       6.2.2. fax-message.............................................8
       6.2.3. pager-message...........................................8
       6.2.4. multimedia-message......................................8
       6.2.5. text-message............................................8
       6.2.6. none....................................................8
   7. Security Considerations.........................................9
   8. IANA Considerations.............................................9
     8.1. Message Content Type Registrations..........................9
     8.2. Registration Template......................................10
     8.3. Message-Context Registration...............................11
   9. APPENDIX: Some messaging scenarios.............................12
     9.1. Internet e-mail............................................12
     9.2. Pager service..............................................12
     9.3. Facsimile..................................................13
     9.4. Voice mail.................................................14
     9.5. Multimedia message.........................................14
   10. References....................................................15
     10.1 Normative References.......................................15
     10.2 Informative References.....................................15
   11. Acknowledgments...............................................15
   12. Authors' Addresses............................................16
   13. Full Copyright Statement......................................17
*1. Introduction
]PRE]

[PRE[
   This document describes a mechanism to allow senders of an Internet
   mail message to convey the message's contextual information.  Taking
   account of this information, the receiving user agent (UA) can make
   decisions that improve message presentation for the user in the
   context the sender and receiver expects.
]PRE]

[PRE[
   In this document, the "message context" conveys information about the
   way the user expects to interact with the message.  For example, a
   message may be e-mail, voice mail, fax mail, etc.  A smart UA may
   have specialized behavior based on the context of the message.
]PRE]

[PRE[
   This document specifies a RFC 2822 header called "Message-Context".
]PRE]

[PRE[
   The mechanism is in some ways similar to the use of the Content-
   Disposition MIME entity described in [6].  Content-Disposition gives
   clues to the receiving User Agent (UA) for how to display a given
   body part.  Message-Context can give clues to the receiving UA for
   the presentation of the message.  This allows the receiving UA to
   present the message to the recipient, in a meaningful and helpful
   way.
]PRE]

[PRE[
   Typical uses for this mechanism include:
]PRE]

[PRE[
   o  Selecting a special viewer for a given message.
]PRE]

[PRE[
   o  Selecting an icon indicating the kind of message in a displayed
      list of messages.
]PRE]

[PRE[
   o  Arranging messages in an inbox display.
]PRE]

[PRE[
   o  Filtering messages the UA presents when the user has limited
      access.
]PRE]


* 2. Conventions used in this document [INS[この文書で使う記法]]

> This document refers generically to the sender of a message in the
masculine (he/him/his) and the recipient of the message in the
feminine (she/her/hers).  This convention is purely for convenience
and makes no assumption about the gender of a message sender or recipient.

この文書では、__&&message&&__の送信者を男性 (彼)
とし、__&&message&&__の受信者を女性 (彼女) として言及します。
この記法は単に便宜上のものであって、__&&message&&__の送受信者の性別について何らの仮定をするものでもありません。

> The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119 [2].
__&&JA:RFCKeywordsAre...&&__> FORMATTING NOTE: Notes, such at this one, provide additional
nonessential information that the reader may skip without missing
anything essential.  The primary purpose of these non-essential notes
is to convey information about the rationale of this document, or to
place this document in the proper historical or evolutionary context.
Readers whose sole purpose is to construct a conformant
implementation may skip such information.  However, it may be of use
to those who wish to understand why we made certain design choices.

整形について: このような注記は、非本質的な追加情報を提供するもので、
読者は本質的な事項を見落とすことなく読み飛ばすことが出来ます。
この非本質的な注記の主たる目的はこの文書の論理的根拠を伝えることやこの文書を適当な歴史的・進化上の位置に置くことです。
適合する実装を構築することだけが目的である読者はそのような情報を読み飛ばすことが出来ます。
しかし、どうしてこのような設計が選ばれたのかを理解したいと思う読者には役に立つことでしょう。


* 3. Motivation [INS[動機]]

> Multimedia messaging systems receive messages that a UA may present
in variety of ways.  For example, traditional e-mail uses simple text
messages that the recipient displays and edits.  One UA may
automatically print Fax images.  Another UA may play voice messages
through a telephone handset.  Likewise, a receiving desktop computer
may process or present documents transferred over e-mail using a
local application.  Emerging and future developments may deliver
other forms of information that have their own characteristics for
user presentation, such as video messages and pager messages.
__&&multimedia&&____&&message system&&__は UA が種々の方法で表現し得る__&&message&&__を受信します。
例えば、伝統的な__&&email&&__は、受信者が表示・編集する単純な__&&text&&____&&message&&__を使います。
ある UA は自動的に__&&fax&&__画像を印刷するかもしれません。
他の UA は電話受話器を通じて__&&voice&&____&&message&&__を再生するかもしれません。
同様に、受信した__&&desktop computer&&__は__&&email&&__で転送された文書を__&&local application&&__を使って処理又は表現するかもしれません。
現在及び将来の開発者は__&&voice&&____&&message&&__や__&&pager&&____&&message&&__のように利用者への表現の性質を持った他の形式の情報を配送するかもしれません。

> An often-requested characteristic for multimedia messaging systems is
to collect received messages in a "universal inbox", and to offer
them to the user as a combined list.
__&&multimedia&&____&&message system&&__でよく要求される性質は、受信__&&message&&__を「__&&universal inbox&&__」に集めて、これを利用者に複合__&&list&&__として提供することです。

> In the context of "unified messaging", different message contexts may
have different implied semantics.  For example, some users may
perceive voicemail to have an implicit assumption of urgency.  Thus
they may wish to gather them together and process them before other
messages.  This results in the end-user receiving agent needing to be
able to identify voicemail and distinguish it from other messages.

「__&&unified messaging&&__」の文脈では、異なる__&&message&&__文脈が異なる暗の意味を持ち得ます。
例えば、ある利用者は__&&voice&&____&&mail&&__を暗に緊急性を持つものとして理解するかもしれません。
従ってそうした利用者はそれを集めて他の__&&message&&__より先に処理することを望むでしょう。
この結果__&&end user&&__の受信__&&agent&&__は__&&voice&&____&&mail&&__を識別して他の__&&message&&__から区別することが出来る必要があります。

> The uses of this kind of presentation characteristic for each message
are multi-fold:

この種の各__&&message&&__の表現性質の利用は複数組まれています。

[PRE[
   o  Display an indication to the user (e.g., by a suitably evocative
      icon along with other summary fields),
]PRE]

[PRE[
   o  Auto-forward a given message type into another messaging
      environment (e.g., a page to a mobile short message service),
]PRE]

[PRE[
   o  Prioritize and group messages in an inbox display list,
]PRE]

[PRE[
   o  Suggest appropriate default handling for presentation,
]PRE]

[PRE[
   o  Suggest appropriate default handling for reply, forward, etc.
]PRE]

- 利用者への案内を表示 (例えば、他の要約欄に適当な呼起し__&&icon&&__で。)
- ある__&&message&&__型を他の__&&message&&__環境に自動転送 
(例えば、携帯の短めの__&&message service&&__を呼び出す。)
- __&&inbox&&__表示__&&list&&__内での__&&message&&__の優先順序付けや分類
- 適切な表現の既定の取扱いを提案
- 返信, 転送等の既定の取扱いを提案

> A problem faced by multimedia messaging systems is that it is not
always easy to decide the context of a received message.  For
example, consider the following scenarios.
__&&multimedia&&____&&message system&&__が直面している問題は、受信__&&message&&__の文脈を決定するのが必ずしも容易ではないことです。
例えば、次の場面を考えてください。

[PRE[
   o  A message that contains audio and image data:  Is this a fax
      message that happens to have some voice commentary?  Is it a voice
      message that is accompanied by some supplementary diagrams?  Is it
      a fully multimedia message, in which all parts are expected to
      carry equal significance?
]PRE]
__&&voice&&__と画像の__&&data&&__を含んだ__&&message&&__。
これは__&&fax&&__&&message&&__に__&&voice&&__でメモが付いたものでしょうか。
それとも__&&voice&&____&&message&&__に補足の図を付けたものでしょうか。
あるいは完全に__&&multimedia&&__な__&&message&&__で、全ての部分を同様の重要度で伝えることを意図したものでしょうか。

[PRE[
   o  A message containing text and audio data:  Is this e-mail with an
      MP3 music attachment?  Is it a voice message that happens to have
      been generated with an initial text header for the benefit of
      non-voice-enabled e-mail receivers?
]PRE]
__&&text&&__と__&&audio&&__の__&&data&&__を含んだ__&&message&&__。
この__&&email&&__は MP3 音楽を添付したものでしょうか。
それとも__&&voice&&____&&message&&__で__&&voice&&__が使えない__&&email&&__受信者向けの初期__&&text&&____&&header&&__つきで生成された__&&voice&&____&&message&&__でしょうか。

> The message context does relate to the message media content.
However, it is not the same thing.  As shown above, the media type
used in a message is not sufficient to indicate the message context.
One cannot determine a priori which media types to use in alternative
(gateway) messages.  Also, what if the user cares about
distinguishing traditional e-mail text from SMS messages?  They are
both the same media type, text, but they have different user contexts.
__&&message&&__文脈は__&&message&&____&&media&&__文脈とは関係はします。
しかし、これらは同じことではありません。
前に示したように、__&&messsage&&__で使われる__&&media type&&__は__&&message&&__文脈を示す上では重要ではありません。
どの__&&media type&&__を代替 (__&&gateway&&__) __&&message&&__に使うのかの優先度は決定できません。
また、利用者が伝統的な__&&email&&____&&text&&__と SMS __&&message&&__を区別した意図したらどうでしょう。
両者は共に同じ__&&media type&&__の__&&text&&__ですが、異なる利用者文脈を持っています。


* 4. Functional Requirements [INS[機能的要件]]

> The goals stated above lead to the following functional requirements.

以上で述べた目標から次の要件が導かれます。

> For receivers:

受信者について:

[PRE[
   o  Identify a message as belonging to a message class.
]PRE]

[PRE[
   o  Incorrect or invalid message classification must not result in
      failure to transfer or inability to present a message.
]PRE]

- __&&message&&__が__&&message class&&__に属するものとして識別する
- 正しくない又は不正な__&&message&&__分類のために転送に失敗したり__&&message&&__の表現が出来なかったりしてはならない

> For senders:

送信者について:

[PRE[
   o  Specify message classes by the originating user's choice of
      authoring tool or simple user interaction.
]PRE]

- 作成する利用者の__&&authoring tool&&__や単純な利用者の動作による選択で__&&message class&&__を指定

> For both:

両者について:

[PRE[
   o  Specify a well-defined set of message classes to make
      interoperability between mail user agents (UAs) possible.
]PRE]

[PRE[
   o  Message classification information has to be interpretable in
      reasonable fashion by many different user agent systems.
]PRE]

[PRE[
   o  The mechanism should be extensible to allow for the introduction
      of new kinds of messages.
]PRE]

- __&&message class&&__のよく定義された集合を指定して__&&mail&&____&&user agent&&__
(UA) 間の相互通信性を可能な限り確保する
- __&&message&&__分類情報は多くの異なる__&&user agent&&____&&system&&__で道理的方法で解釈可能でなければならない
- その仕組みは拡張可能で新しい種類の__&&message&&__を導入可能とする

[PRE[
   NOTE: We specifically do not specify user agent behavior when the
   user agent forwards a message.  Clearly, the user agent, being
   message-context-aware, should provide a meaningful message-context.
   It is obvious what to do for the easy cases.  Messages that the user
   simply forwards will most likely keep the context unchanged.
   However, it is beyond the scope of this document to specify the user
   agent behavior for any other scenario.
]PRE]

注意: 私達は、__&&user agent&&__が__&&message&&__を転送する時の__&&user agent&&__の動作を具体的には規定しません。
明らかに、__&&user agent&&__で__&&message&&__文脈を知っているものは、意味のある__&&message&&__文脈を提供するべきです。
簡単な場合には何をするのかは自明です。
利用者が単に転送する__&&message&&__では文脈は変更しないでおくのが最も適当でしょう。
しかし、他の場面での__&&user agent&&__の動作についてはこの文書の適用範囲外です。


* 5. Determining the Message Context [INS[__&&message&&__文脈の決定]]

> One method of indicating the interpretation context of a message is
to examine the media types in the message.  However, this requires
the UA to scan the entire message before it can make this
determination.  This approach is particularly burdensome for the
multi-media mail situation, as voice and especially video mail
objects are quite large.

解釈した__&&message&&__の文脈を示す一つの方法は、__&&message&&__中の__&&media type&&__を検査することです。
しかし、このために UA は、この決定をする前に__&&message&&__全体を走査しなければなりません。
この方法は特に__&&multimedia&&____&&mail&&__の場合には重荷となります。
__&&voice&&__や特に__&&video&&__の__&&mail&&____&&object&&__は非常に大きくなりますから。

> We considered indicating the message context by registering a
multipart/* MIME subtype (Content-Type).  For example, the VPIM Work
Group has registered multipart/voice-message to indicate that a
message is primarily voice mail [7].  However, 
multipart/voice-message is identical in syntax to multipart/mixed.  The only
difference is that VPIM mail transfer agents and user agents
recognize that they can perform special handling of the message based
on it being a voice mail message.  Moreover, Content-Type refers to a
given MIME body part, not to the message as a whole.

[CODE[multipart/*]] MIME __&&subtype&&__ ([CODE[Content-Type]])
を登録することで__&&message&&__文脈を示すことも考えました。例えば、
VPIM __&&work group&&__はある__&&message&&__が主として__&&voice&&____&&mail&&__であることを示すために
[CODE[multipart/voice-message]] を登録しました。
しかし、 [CODE[multipart/voice-message]] は [CODE[multipart/mixed]]
の構文と同一です。唯一の違いは、 VPIM __&&mail&&__転送__&&agent&&__及び__&&user agent&&__がその__&&message&&__を__&&voice&&____&&mail&&____&&message&&__であることに基づいた特別な__&&message&&__の取扱いを行うことが出来ると認識することです。
更に、 [CODE[Content-Type]] は当該 MIME __&&body part&&__にのみ言及するのであって、__&&message&&__全体に言及するのではありません。

[INS[

訳注: 構文が同じというのは、そもそも [[RFC2046]] がそう規定している
([[multipart/*]] 参照。) からであって当然のことです。 [INS[(スコア -1: 余計なもの)]]
]INS]

> We wish to avoid scanning the entire message.  In addition, we wish
to avoid having to create multiple aliases for multipart/mixed every
time someone identifies a new primary content type.  Multiple aliases
for multipart/mixed are not desirable as they remove the possibility
for specifying a message as multipart/alternate, multipart/parallel,
or multipart/encrypted, for example.
__&&message&&__の全体を走査することは避けたいと願っています。
加えて、誰かが新しい主__&&content type&&__を識別する旅に複数の
[CODE[multipart/mixed]] の別名を作成しなければならないのは避けたいと願っています。
複数の [CODE[multipart/mixed]] の別名は、__&&message&&__を
[CODE[multipart/alternate]], [CODE[multipart/parallel]],
[CODE[multipart/encrypted]] などとして指定する時の可搬性を損ないますから望ましくありません。

> Since the message context is an attribute of the entire message, it
is logical to define a new top-level (RFC 2822 [3]) message
attribute.  To this end, this document introduces the message
attribute "Message-Context".
__&&message context&&__は__&&message&&__全体の属性ですから、
新しい__&&top-level&&__ (RFC 2822) __&&message&&__属性を定義するのは論理的です。
この結論から、この文書は__&&message&&__属性 [CODE[Message-Context]]
を導入します。

> Message-Context only serves to identify the message context.  It does
not provide any indication of content that the UA must be capable of
delivering.  It does not imply any message disposition or delivery
notification.  There is a related effort to define Critical Content
of Internet Mail [8] that one might use to perform these tasks.
__&&Message-Context&&__は、__&&message context&&__の識別のみのために供給されます。
これは UA が配送の能力を持っていなければならない内容を指示するものではありません。
これはいかなる__&&message disposition&&__や__&&delivery notification&&__を課すものでもありません。
こうした作業を行うのに使えるものとしては、関連して__&&Internet Mail&&__の__&&Critical Content&&__を定義する仕事があります。

> Message-Context is only an indicator.  We do not intend for it to
convey information that is critical for presentation of the message.
One can conceive of goofy situations, such as a message marked
"voice-message" but without an audio body part.  In this case, the
fact that the contents of a message don't match its context does not
mean the receiving system should generate an error report or fail to
deliver or process the message.
__&&Message-Context&&__は単なる指示子です。
これを__&&message&&__の表現に__&&ritical&&__であることの情報を運ぶのは意図していません。
[CODE[voiced-message]] と__&&mark&&__されているのに__&&audio&&____&&body part&&__がないようなおかしな状況もあるかもしれません。
この場合、__&&message&&__の内容がその__&&context&&__に一致しなかったという事実は、
受信した__&&system&&__が__&&error report&&__を生成したり__&&message&&__を配送したり処理したりするのに失敗したりする__&&should&&__ということは意味しません。


* 6. Message-Context Reference Field [INS[__&&Message-Context&&____&&reference&&____&&field&&__]]

> The Message-Context reference field is a top-level header inserted by
the sending UA to indicate the context of the message.

[CODE[Message-Context]] __&&reference&&____&&field&&__は、
送信 UA により__&&message&&__の__&&context&&__を示すために挿入される__&&top-level&&____&&header&&__です。

> A receiving user agent MUST NOT depend on the indicated 
message-context value in a way that prevents proper presentation of the
message.  If the value is incorrect or does not match the message
content, the receiving user agent MUST still be capable of displaying
the message content at least as meaningfully as it would if no
Message-Context value were present.

受信__&&user agent&&__は、__&&message&&__の適当な__&&presentation&&__を妨げる形で示された__&&message-context&&__値に依存しては__&&MUST NOT&&__。
値が間違っているか__&&message&&__内容と一致しない時でも、
受信した__&&user agent&&__は依然__&&message&&__内容を、
少なくても [CODE[Message-Context]] 値が指定されていなかった場合と同程度には有意に表示できる能力がなければ__&&MUST&&__。

> One can envision situations where a well-formed message ends up not
including a media type one would expect from the message-context.
For example, consider a voice messaging system that records a voice
message and also performs speech-to-text processing on the message.
The message then passes through a content gateway, such as a
firewall, that removes non-critical body parts over a certain length.
The receiving user agent will receive a message in the voice-message
context that has only a text part and no audio.  Even though the
message does not have audio, it is still in the voice message context.

[PRE[
   Said differently, the receiving UA can use the message-context to
   determine whether, when, and possibly where to display a message.
   However, the message-context should not affect the actual rendering
   or presentation.  For example, if the message is in the voice-message
   context, then don't try to send it to a fax terminal.  Conversely,
   consider the case of a message in the voice-message context that gets
   delivered to a multimedia voice terminal with a printer.  However,
   this message only has fax content.  In this situation, the "voice-
   message" context should not stop the terminal from properly rendering
   the message.
]PRE]

6.1. Message-Context Syntax

[PRE[
   The syntax of the Message-Context field, described using the ABNF [4]
   is as follows.  Note that the Message-Context header field name and
   message-context-class values are not case sensitive.
]PRE]

[PRE[
      "Message-Context" ":" message-context-class CRLF
]PRE]

6.2. message-context-class Syntax

[PRE[
   The message-context-class indicates the context of the message.  This
   is an IANA registered value.  Current values for message-context-
   class are as follows.
]PRE]

Burger, et al.              Standards Track                     [Page 7]

RFC 3458           Message Context for Internet Mail        January 2003

[PRE[
      message-context-class =  (   "voice-message"
                                 / "fax-message"
                                 / "pager-message"
                                 / "multimedia-message"
                                 / "text-message"
                                 / "none"
                                )
]PRE]

[PRE[
   Note: The values for Message-Context MUST be IANA registered values
   following the directions in the IANA Considerations section below.
]PRE]

6.2.1. voice-message

[PRE[
   The voice-message class states the message is a voice mail message.
]PRE]

6.2.2. fax-message

[PRE[
   The fax-message class states the message is a facsimile mail message.
]PRE]

6.2.3. pager-message

[PRE[
   The pager-message class states the message is a page, such as a text
   or numeric pager message or a traditional short text message service
   (SMS) message.
]PRE]

6.2.4. multimedia-message

[PRE[
   The multimedia-message class states the message is an aggregate
   multimedia message, such as a message specified by [9].  This helps
   identify a message in a multimedia context.  For example, a MIME
   multipart/related [10] data part and resource part looks the same as
   a multimedia MHTML multipart/related.  However, the semantics are
   quite different.
]PRE]

6.2.5. text-message

[PRE[
   The text-message class states the message is a traditional internet
   mail message.  Such a message consists of text, possibly richly
   formatted, with or without attachments.
]PRE]

6.2.6. none

[PRE[
   The none class states there is no context information for this
   message.
]PRE]

[PRE[
   If a message has no Message-Context reference field, a receiving user
   agent MUST treat it the same as it would if the message has a "none"
   value.
]PRE]

Burger, et al.              Standards Track                     [Page 8]

RFC 3458           Message Context for Internet Mail        January 2003

7. Security Considerations

[PRE[
   The intention for this header is to be an indicator of message
   context only.  One can imagine someone creating an "Application"
   Message-Context.  A poorly designed user agent could blindly execute
   a mailed program based on the Message-Context.  Don't do that!
]PRE]

[PRE[
   One can envision a denial of service attack by bombing a receiver
   with a message that has a Message-Context that doesn't fit the
   profile of the actual body parts.  This is why the receiver considers
   the Message-Context to be a hint only.
]PRE]

8. IANA Considerations

[PRE[
   Section 8.3 is a registration for a new top-level RFC 2822 [3]
   message header, "Message-Context".
]PRE]

[PRE[
   This document creates an extensible set of context types.  To promote
   interoperability and coherent interpretations of different types, a
   central repository has been established for well-known context types.
]PRE]

[PRE[
   The IANA has created a repository for context types called "Internet
   Message Context Types".  Following the policies outlined in [5], this
   repository is "Specification Required" by RFC.  Section 8.1 describes
   the initial values for this registry.
]PRE]

[PRE[
   To create a new message context type, you MUST publish an RFC to
   document the type.  In the RFC, include a copy of the registration
   template found in Section 8.2 of this document.  Put the template in
   your IANA Considerations section, filling-in the appropriate fields.
   You MUST describe any interoperability and security issues in your
   document.
]PRE]

8.1. Message Content Type Registrations

[PRE[
   Internet Message Content Types
   ==============================
]PRE]

[PRE[
   Value              Description                           Reference
   -----              -----------                           ---------
   voice-message      Indicates a message whose primary     This RFC
                      content is a voice mail message.  The
                      primary content is audio data.  The
                      context is usually a message recorded
                      from a voice telephone call.
]PRE]

Burger, et al.              Standards Track                     [Page 9]

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[PRE[
   fax-message        Indicates a message whose primary     This RFC
                      content is a fax mail message.  The
                      primary content is image data.  The
                      context is usually a message recorded
                      from a facsimile telephone call.
]PRE]

[PRE[
   pager-message      Indicates a message whose primary     This RFC
                      content is a page.  The primary
                      content is text data.  The context is
                      an urgent message usually of a
                      limited length.
]PRE]

[PRE[
   multimedia-message Indicates a message whose primary     This RFC
                      content is a multimedia message.  The
                      primary content is multimedia, most
                      likely MHTML.  The context is often
                      spam or newsletters.
]PRE]

[PRE[
   text-message       Indicates a classic, text-based,      This RFC
                      Internet message.
]PRE]

[PRE[
   None               Indicates an unknown message context. This RFC
]PRE]

8.2. Registration Template

[PRE[
   In the following template, a pipe symbol, "|", precedes instructions
   or other helpful material.  Be sure to replace "<classname>" with the
   class name you are defining.
]PRE]

[PRE[
   Message-Context class name:
   <classname>
]PRE]

[PRE[
   Summary of the message class:
       | Include a short (no longer than 4 lines) description or summary
       | Examples:
       |   "Palmtop devices have a 320x160 pixel display, so we can..."
       |   "Color fax is so different than black & white that..."
   Person & email address to contact for further information:
       | Name & e-mail
]PRE]

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&#12;
RFC 3458           Message Context for Internet Mail        January 2003

8.3. Message-Context Registration

   To: iana@iana.org
   Subject: Registration of New RFC 2822 Header

   RFC 2822 Header Name:
   Message-Context

   Allowable values for this parameter:
   Please create a new registry for Primary Context Class
   registrations.  See section 8.1 of this document for the initial
   values.

   RFC 2822 Section 3.6 Repeat Value:
   Field             Min Number   Max Number   Notes
   Message-Context       0            1

   Person & email address to contact for further information:
   Eric Burger
   e.burger@ieee.org































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9. APPENDIX: Some messaging scenarios

   This section is not a normative part of this document.  We include it
   here as a historical perspective on the issue of multimedia message
   types.

   These scenarios are neither comprehensive nor fixed.  For example,
   e-mails being typically text-based do not mean that they cannot
   convey a voice-message.  This very mutability serves to underline the
   desirability of providing some explicit message context hint.

9.1. Internet e-mail

   Internet e-mail carries textual information.  Sometimes it conveys
   computer application data of arbitrary size.

   Typically, one uses e-mail for non-urgent messages, which the
   recipient will retrieve and process at a time convenient to her.

   The normal device for receiving and processing e-mail messages is
   some kind of personal computer.  Modern personal computers usually
   come with a reasonably large display and an alphanumeric keyboard.
   Audio, video, and printing capabilities are not necessarily
   available.

   One can use E-mail for communication between two parties (one-to-
   one), a small number of known parties (one-to-few) or, via an e-mail
   distribution list, between larger numbers of unknown parties (one-
   to-many).

   One of the endearing characteristics of e-mail is the way that it
   allows the recipient to forward all or part of the message to another
   party, with or without additional comments.  It is quite common for
   an e-mail to contain snippets of content from several previous
   messages.  Similar features apply when replying to e-mail.

9.2. Pager service

   One uses a pager message to convey notifications and alerts.  For the
   most part, these notifications are textual information of limited
   size.  The typical limit is 160 characters.  People use pages for
   relatively urgent messages, which the sender wishes the receiver to
   see and possibly respond to within a short time period.  Pager
   messages are often used as a way of alerting users to something
   needing their attention.  For example, a system can use a page to
   notify a subscriber there is a voicemail message requiring her
   attention.




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   Example devices for sending and receiving a pager message are a
   mobile telephone with a small character display or a text pager.
   Personal computers and personal digital assistants (PDAs) can also
   participate in pager messaging.

   Currently, the most common use of pager messages are between just two
   parties (one-to-one).

   One delivery method for pager messages is the short text messaging
   service (SMS).  SMS is a facility that has evolved for use with
   mobile telephones, and has an associated per-message transmission
   charge.  Note that the focus here is on the notification aspect of
   SMS.  From the beginning, SMS was envisioned to be more than a simple
   pager service.  Operators can use SMS to provision the phone, for
   example.  From the subscriber point of view, SMS has evolved
   considerably from its origins as a pure pager replacement service.
   For example, with mobile originate service, people can have two-way
   text chat sessions using SMS and a mobile phone.  In addition, there
   are SMS-enabled handsets that can display pictures.  However, for the
   purposes of this document, there is still a need to capture the
   essence of a "highly urgent, short-text, notification or alert"
   service.

   Users often send pager messages in isolation, rather than as part of
   a longer exchange.  One use for them is as a prompt or invitation to
   communicate by some more convenient and content-rich method, such as
   a telephone call.

9.3. Facsimile

   People use facsimile to convey image information of moderate size,
   typically a small number of pages.  Sometimes people use facsimile
   for larger documents.

   Facsimile is a facility that usually uses circuit-switched telephone
   circuits, with connection-time charges.  Message transfer takes place
   in real-time.  Thus, people often use facsimile for urgent
   communication.

   The normal device for sending and receiving a facsimile is a self-
   contained scanning and printing device connected to a telephone line
   or a desktop computer.

   Most facsimiles are between just two parties (one-to-one).  However,
   a significant portion of facsimile service is broadcast between
   multiple parties (one-to-many).





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   Most facsimile exchanges are in isolation, rather than as part of a
   longer exchange.  Facsimile data is typically not suitable for
   further processing by computer.

9.4. Voice mail

   People use voice mail to convey audio information, almost exclusively
   human speech.

   Voice mail is a facility that usually uses circuit-switched telephone
   circuits, with modest connection-time charges, often used for
   moderately urgent messages.  A common use for them is as a prompt or
   invitation to communicate by some more convenient method, such as a
   telephone call.  In most, but not all cases, the sender of a voice
   message does not want to send a message at all.  Rather, they wished
   to engage in a real-time conversation.

   The normal device for sending and receiving a voice mail is a
   telephone handset.

   Voice messages are usually sent between just two parties (one-to-
   one).

   Voice mail data is not generally suitable for further processing by
   computer.

9.5. Multimedia message

   We define a multimedia message as a message containing more than one
   basic media type (text, image, audio, video, model, application).

   The following are some characteristics of a multimedia message.

   In some cases, a multimedia message is just e-mail with an attachment
   that a multimedia display application presents.  For example, I can
   send you an MP3 of something I recorded in my garage today.

   In other cases, a multimedia message represents a convergence between
   two or more of the scenarios described above.  For example, a voice
   message with an accompanying diagram or a talking head video message
   is a multimedia message.

   The characteristics will vary somewhat with the intent of the sender.
   This in turn may affect the user agent or application used to render
   the message.






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10. References

10.1 Normative References

   [1]  Bradner, S., "The Internet Standards Process -- Revision 3", BCP
        9, RFC 2026, October 1996.

   [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [3]  Resnick, P., "Internet Message Format", RFC 2822, April 2001.

   [4]  Crocker, D. and P. Overell, Eds., "Augmented BNF for Syntax
        Specifications: ABNF", RFC 2234, November 1997.

   [5]  Alvestrand, H. and T. Narten, "Guidelines for Writing an IANA
        Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.

10.2 Informative References

   [6]  Troost, R., Dorner, S. and K. Moore, "Communicating Presentation
        Information in Internet Messages: The Content-Disposition Header
        Field", RFC 2183, August 1997.

   [7]  Vaudreuil, G. and G. Parsons, "VPIM Voice Message MIME Sub-type
        Registration", RFC 2423, September 1998.

   [8]  Burger, E., "Critical Content of Internet Mail", RFC 3459,
        January 2003.

   [9]  Palme, J., Hopmann, A. and N. Shelness, "MIME Encapsulation of
        Aggregate Documents, such as HTML (MHTML)", RFC 2557, March
        1999.

   [10] Levinson, E., "The MIME Multipart/Related Content-type", RFC
        2387, August 1998.

11. Acknowledgments

   Many of the ideas here arose originally from a discussion with Jutta
   Degener.

   We'd also like to thank Keith Moore for helping us tighten-up our
   explanations.

   In the last round, we got some rather good advise from Caleb Clausen
   and Dave Aronson.




Burger, et al.              Standards Track                    [Page 15]

 
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   Antti Vaha-Sipila pointed out advances in SMS, while Stuart McRae
   helped distil the essence of the pager service vis a vis SMS.

   We offer an extra special thanks to Greg Vaudreuil for pulling RFC
   2557 out of his hat.

12. Authors' Addresses

   Eric Burger
   SnowShore Networks, Inc.
   285 Billerica Rd.
   Chelmsford, MA  01824-4120
   USA

   Phone: +1 978 367 8403
   EMail: e.burger@ieee.org


   Emily Candell
   Comverse Network Systems
   200 Quannapowitt Pkwy.
   Wakefield, MA  01880
   USA

   Phone: +1 781 213 2324
   EMail: emily.candell@comverse.com


   Graham Klyne
   Nine by Nine
   United Kingdom

   EMail: GK-IETF@ninebynine.org


   Charles Eliot
   Microsoft Corporation
   One Microsoft Way
   Redmond WA 98052
   USA

   Phone: +1 425 706 9760
   EMail: charle@Microsoft.com








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13.  Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















Burger, et al.              Standards Track                    [Page 17]


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