RFC 2387

RFC 2387

[3] multipart/related も参照。

The MIME Multipart/Related Content-type

Status of this Memo

This memo defines an Experimental Protocol for the Internet community. This memo does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested. Distribution of this memo is unlimited.

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 (1998).  All Rights Reserved.


The Multipart/Related content-type provides a common mechanism for representing objects that are aggregates of related MIME body parts. This document defines the Multipart/Related content-type and provides examples of its use.

* 1.  Introduction
>     Several applications of MIME, including MIME-PEM, and MIME-Macintosh
and other proposals, require multiple body parts that make sense only
in the aggregate.  The present approach to these compound objects has
been to define specific multipart subtypes for each new object.  In
keeping with the MIME philosophy of having one mechanism to achieve
the same goal for different purposes, this document describes a
single mechanism for such aggregate or compound objects.

MIME PEMMacMIME やその他の提案など幾つかの MIME応用は集積のためだけに複数本体部分を必要としています。 このような合成物体に現在採られているのは新しい物体それぞれに特定の多部分部分型を定義するという方法です。 この文書は、集積・合成物体のための、 異なる目的で同じ目標を達成するための1つの仕組みを持つという MIME の精神を守った一つの仕組みを説明します。

>     The Multipart/Related content-type addresses the MIME representation
of compound objects.  The object is categorized by a "type"
parameter.  Additional parameters are provided to indicate a specific
starting body part or root and auxiliary information which may be
required when unpacking or processing the object.

multipart/related 内容型は合成物体の MIME 表現を表します。物体は type 引数により分類します。特定の開始本体部分 () を示す引数や物体を取出し・処理する時に必要な補助情報のための引数も提供します。

Multipart/Related MIME entities may contain Content-Disposition headers that provide suggestions for the storage and display of a body part. Multipart/Related processing takes precedence over Content-Disposition; the interaction between them is discussed in section 4.

multipart/related MIME 実体は本体部分の蓄積と表示に関する提案を行う Content-Disposition 頭を含んでも構いません。 multipart/related 処理は Content-Disposition より優先します。両者の関係は4章で議論します。

Responsibility for the display or processing of a Multipart/Related's constituent entities rests with the application that handles the compound object.

multipart/related を構成する実体の表示・処理の責任は豪勢物体を扱う応用にあります。

2. Multipart/Related Registration Information

The following form is copied from RFC 1590, Appendix A.

次の書式は RFC 1590 附属書 A から複写しました。

  • To: IANA@isi.edu
  • Subject: Registration of new Media Type content-type/subtype
  • Media Type name: Multipart
  • Media subtype name: Related
  • Required parameters: Type, a media type/subtype.
  • Optional parameters: Start, a content-id.
                                  Start-info, a string or content-id list.
    -     Encoding considerations:   Multipart content-types cannot have encodings.
    -     Security considerations:   Depends solely on the referenced type.
    -   Published specification:   This document. RFC-REL (this document).
    -     Person & email address to contact for further information:
    Edward Levinson
    Accurate Information Systems, Inc.
    2 Industrial Way
    Eatontown, NJ 07724
    +1 908 389 5550
    +1 908 389 5556 (fax)
    47 Clive Street
    Metuchen, NJ 08840-1060
    +1 908 494 1606

3. Intended usage

The Multipart/Related media type is intended for compound objects consisting of several inter-related body parts. For a Multipart/Related object, proper display cannot be achieved by individually displaying the constituent body parts. The content-type of the Multipart/Related object is specified by the type parameter. The "start" parameter, if given, points, via a content-ID, to the body part that contains the object root. The default root is the first body part within the Multipart/Related body.

multipart/related 媒体型は複数の関係のある本体部分から成る合成物体を想定しています。 multipart/related 物体では構成する本体部分を個々に表示するだけでは適切な表示とは言えません。 multipart/related 物体の内容型は type 引数で指定します。 start 引数があれば、 内容ID によって物体を含む本体部分を表します。 既定の根は multipart/related 本体の中の最初の本体部分です。

The relationships among the body parts of a compound object distinguishes it from other object types. These relationships are often represented by links internal to the object's components that reference the other components. Within a single operating environment the links are often file names, such links may be represented within a MIME message using content-IDs or the value of some other "Content-" headers.

合成物体の本体部分間の関係は他の物体型と異なります。 関係はよく物体の部品の内部で他の部品を指す連結で表現されます。 一つの操作環境の中では連結はしばしばファイル名であり、 そのような連結は MIME メッセージ中では内容ID や他の Content-* 頭の値で表現されるかもしれません。

3.1. The Type Parameter

The type parameter must be specified and its value is the MIME media type of the "root" body part. It permits a MIME user agent to determine the content-type without reference to the enclosed body part. If the value of the type parameter and the root body part's content-type differ then the User Agent's behavior is undefined.

type 引数は指定しなければならず、 その値は本体部分MIME 媒体型です。この引数により MIME 利用者エージェントは囲まれた本体部分を参照しなくても内容型を決定できます。 type 引数の値と根本体部分の内容型が異なる時の利用者エージェントの動作は未定義です。

Note: Constraining the "type" parameter's value to an existing media type allows the appropriate processing to be identified without creating yet another hierarchy of registered types. A possible default action would have the MIME mail User Agent (MUA) to display the "start" entity alone when it could process the media type as a basic type but not as Multipart/Related.

注意: type 引数の値を既存の媒体型に制約することで、 新しい登録型階層を作らずに適切な処理を識別できます。 MIME メイル利用者エージェント (MUA) が媒体型を基本型としては処理できるものの multipart/related としては処理できない時に start 実体だけを表示するのを既定の動作ともできるでしょう。

3.2. The Start Parameter

The start parameter, if given, is the content-ID of the compound object's "root". If not present the "root" is the first body part in the Multipart/Related entity. The "root" is the element the applications processes first.

start 引数は、指定された場合、 合成物体の内容ID です。 存在しない場合multipart/related 実体の中の最初の本体部分です。は最初に応用が処理する要素です。

In the case of a Multipart/Alternative body part containing several entities with identical content-IDs the start entity should be selected using the Multipart/Alternative rules.

multipart/alternative 本体部分の場合で複数の実体が同じ内容 ID を持っている時は、 multipart/alternative の規則により開始実体を選択するべきです。

Note: The "start" parameter allows for types in which the root element gets generated by the sending application, perhaps on the fly. Such an application can create the "start" content-id when processing begins and then insert the body part when it is complete.

注意: start 引数は根要素が送信応用によりおそらくはその場で生成されるような型も認めます。 そのような応用は処理が始まる時に start 内容 ID を作成して、処理が完了してから本体部分を挿入することができます。

3.3. The Start-Info Parameter

Additional information can be provided to an application by the start-info parameter. It contains either a string or points, via a content-ID, to another MIME entity in the message. A typical use might be to provide additional command line parameters or a MIME entity giving auxiliary information for processing the compound object.

応用は追加情報を start-info 引数で提供できます。この引数は文字列か内容 ID によるメッセージ中の他の MIME 実体の参照のいずれかを含みます。 追加の命令行引数の提供や豪勢物体の処理のための補助情報を提供する MIME 実体の指定が典型的な例です。

Applications that use Multipart/Related must specify the interpretation of start-info. User Agents shall provide the parameter's value to the processing application. Processes can distinguish a start-info reference from a token or quoted-string by examining the first non-white-space character, "<" indicates a content-id reference.

multipart/related を使う応用は start-info の解釈を規定しなければなりません。利用者エージェントは引数値を処理応用に提供しなければなりません。 start-info の参照と字句や引用文字列は最初の非空白文字を調べれば区別できます。 最初の文字が < であれば参照です。

3.4. Syntax

       related-param    := [ ";" "start" "=" cid ]
                           [ ";" "start-info"  "="
                             ( cid-list / value ) ]
                           [ ";" "type"  "=" type "/" subtype ]
                           ; order independent
       cid-list        := cid cid-list
       cid             := msg-id     ; c.f. [822]
       value           := token / quoted-string    ; c.f. [MIME]
                               ; value cannot begin with "<"

Note that the parameter values will usually require quoting. Msg-id contains the special characters "<", ">", "@", and perhaps other special characters. If msg-id contains quoted-strings, those quote marks must be escaped. Similarly, the type parameter contains the special character "/".

注意: 引数値は通常引用が必要です。 msg-id は特殊文字 <, >, @ を含みますし、おそらく他の特殊文字も含むでしょう。 msg-id が引用文字列を含む場合、その引用符を逃避しなければなりません。 同様に、 type 引数は特殊文字 / を含みます。

4. Handling Content-Disposition Headers

Content-Disposition Headers [DISP] suggest presentation styles for MIME body parts. [DISP] describes two presentation styles, called the disposition type, INLINE and ATTACHMENT. These, used within a multipart entity, allow the sender to suggest presentation information. [DISP] also provides for an optional storage (file) name. Content-Disposition headers could appear in one or more body parts contained within a Multipart/Related entity.

Content-Disposition 頭は MIME 本体部分の表現様式を提案します。 RFC 1806 は表現様式を表す配置型として inline, attachment の2種類を説明しています。 両者は多部分実体の中で使って、送信者が表現情報を提案することができます。 RFC 1806 は省略可能な蓄積域 (ファイル) 名も提供しています。 Content-Disposition 頭は multipart/related 実体に含まれる本体部分の一つ以上に出現できます。

Using Content-Disposition headers in addition to Multipart/Related provides presentation information to User Agents that do not recognize Multipart/Related. They will treat the multipart as Multipart/Mixed and they may find the Content-Disposition information useful.

multipart/relatedContent-Disposition も使うと multipart/related を認識しない利用者エージェントに表現情報を提供することができます。 認識しない利用者エージェントは多部分を multipart/mixed として扱い、 Content-Disposition 情報を役立てるかもしれません。

With Multipart/Related however, the application processing the compound object determines the presentation style for all the contained parts. In that context the Content-Disposition header information is redundant or even misleading. Hence, User Agents that understand Multipart/Related shall ignore the disposition type within a Multipart/Related body part.

しかし、 multipart/related では合成物体を処理する応用が含まれている部分すべての表現様式を決定します。 そのため Content-Disposition 頭の情報は冗長だったり誤解の虞もあったりします。 ですから、 multipart/related を理解する利用者エージェントは multipart/related 本体部分内の配置型を無視しなければなりません。

It may be possible for a User Agent capable of handling both Multipart/Related and Content-Disposition headers to provide the invoked application the Content-Disposition header's optional filename parameter to the Multipart/Related. The use of that information will depend on the specific application and should be specified when describing the handling of the corresponding compound object. Such descriptions would be appropriate in an RFC registering that object's media type.

multipart/relatedContent-Disposition 頭の両方を扱うことのできる利用者エージェントは呼出す応用multipart/relatedContent-Disposition 頭の省略可能な filename 引数を提供することも可能でしょう。 この情報を使うかは各応用に依存し、対応する合成物体の扱いを説明する時に規定するべきです。 その説明は物体の媒体型を登録する RFC で行うのが適切でしょう。

4. 5. Examples

4.1 5.1 Application/X-FixedRecord

The X-FixedRecord content-type consists of one or more octet-streams and a list of the lengths of each record. The root, which lists the record lengths of each record within the streams. The record length list, type Application/X-FixedRecord, consists of a set of INTEGERs in ASCII format, one per line. Each INTEGER gives the number of octets from the octet-stream body part that constitute the next "record".

x-fixedrecord 内容型は一つ以上のオクテット列と各記録の長さの並びから成ります。 根はオクテット列中の各記録の長さを列挙します。 application/x-fixedrecord 型の記録長並びは ASCII 書式の行毎の整数の連続で構成します。各整数はオクテット列本体部分の次の 記録のオクテット数を表します。

The example below, uses a single data block which the sender processes on the fly to generate the record length list. Consequently the list appears after the data.


Content-Type: Multipart/Related; boundary=example-1
        start-info="-o ps"

Content-Type: Application/X-FixedRecord
Content-ID: <950120.aaCC@XIson.com>

Content-Type: Application/octet-stream
Content-Description: The fixed length records
Content-Transfer-Encoding: base64
Content-ID: <950120.aaCB@XIson.com>

Content-Type: Application/X-FixedRecord
Content-ID: <950120.aaCC@XIson.com>


4.2 5.2 Text/X-Okie

The Text/X-Okie is an invented markup language, similar to HTML, that permits permitting the inclusion of images with text. A feature of this example is the inclusion of two additional body parts, both picture. They are referred to internally by the encapsulated document via each picture's body part content-ID. Usage of "cid:", as in this example, may be useful for a variety of compound objects. It is not, however, a part of the Multipart/Related specification.

text/x-okie は架空のマーク付け言語で、 文章に画像を含めることができます。この例では2つの画像の本体部分が含まれています。 本体部分はカプセル化された文書から画像の本体部分の内容 ID で内部的に参照されています。この例のように cid: を使うのは色々な合成物体で便利でしょう。 しかし、これは multipart/related 仕様の一部ではありません。

Content-Type: Multipart/Related; boundary=example-2;

Content-Type: Text/x-Okie; charset=iso-8859-1;
Content-ID: <950118.AEBH@XIson.com>
Content-Description: Document

This picture was taken by an automatic camera mounted ...
{image file=cid:<950118.AECB@XIson.com>}
Now this is an enlargement of the area ...
{image file=cid:<950118:AFDH@XIson.com>}
Content-Type: image/jpeg
Content-ID: <950118.AFDH@XIson.com>
Content-Transfer-Encoding: BASE64
Content-Description: Picture A

[encoded jpeg image]
Content-Type: image/jpeg
Content-ID: <950118.AECB@XIson.com>
Content-Transfer-Encoding: BASE64
Content-Description: Picture B

[encoded jpeg image]

5.3 Content-Disposition

In the above example each image body part could also have a Content-Disposition header. For example,

先の例で各画像本体部分に Content-Disposition 頭も付けることができます。

Content-Type: image/jpeg
Content-ID: <950118.AECB@XIson.com>
Content-Transfer-Encoding: BASE64
Content-Description: Picture B
Content-Disposition: INLINE

[encoded jpeg image]

User Agents that recognize Multipart/Related will ignore the Content-Disposition header's disposition type. Other User Agents will process the Multipart/Related as Multipart/Mixed and may make use of that header's information.

multipart/related を認識する利用者エージェントContent-Disposition 頭の配置型を無視します。他の利用者エージェントは multipart/relatedmultipart/mixed として処理し、 Content-Disposition 頭の情報も利用するかもしれません。

5. 6. User Agent Requirements

User agents that do not recognize Multipart/Related shall, in accordance with [MIME], treat the entire entity as Multipart/Mixed. MIME User Agents that do recognize Multipart/Related entities but are unable to process the given type shall either suppress the entire Multipart/Related body part or process the root alone should give the user the option of suppressing the entire Multipart/Related body part shall be. In either case the user should be notified of the MUA's action.

multipart/related を認識しない利用者エージェントMIME に従い実体全体を multipart/mixed として扱います。 MIME 利用者エージェントで multipart/related 実体を認識するものの与えられた type を処理できないものは、 multipart/related 本体部分全体を抑制する選択肢を利用者に提供するべきです。

Existing MIME-capable mail user agents (MUAs) handle the existing media types in a straightforward manner. For discrete media types (e.g. text, image, etc.) the body of the entity can be directly passed to a display process. Similarly the existing composite subtypes can be reduced to handing one or more discrete types. Handling Multipart/Related differs from other media types in that processing cannot be reduced to handling the individual entities. Existing media types are handled by MIME-capable MUAs handle in a straightforward manner. For basic media types (e.g., text, image, etc.) the body of the entity can be directly passed to a display process. Composite media types can be reduced to handing one or more discrete types.

既存の MIME メイル利用者エージェントは既存の媒体型をそのままの方法で扱います。 分離媒体型 (例えば text/*, image/* など) は実体の本体を直接表示処理に渡すことができます。 同様に既存の合成部分型は一つ以上の分離型として扱うことができます。 multipart/related の扱いは処理を個々の実体に分けることができないという点が異なります。

Multipart/Related provides an irreducible composite media type.

The following sections discuss what information the processing application requires.


It is possible that an application specific "receiving agent" will manipulate the entities, after initial processing by the MIME User Agent, for display prior to invoking actual application process. From the viewpoint of the MUA, the receiving agent is the application. Okie, above, demonstrates is an example of this; it may need a receiving agent to parse the document and substitute local file names for the originator's file names. Other applications may just require a table showing the correspondence between the local file names and the originator's. The receiving agent takes responsibility for such processing.

応用規定の受信エージェントが実際の応用処理を呼出す前に実体を走査することも可能です。 先の Okie はこの例で、受信エージェントは文書を構文解析し、 局所ファイル名を送信者側のファイル名に書き換えます。 他の応用はただ単に局所ファイル名と受信者のファイル名の対応表が必要かもしれません。 受信エージェントはこのような処理の責任を持ちます。

The receiving agent takes responsibility any for such processing.

5.1 6.1 Data Requirements

MIME-capable MUAs mail user agents (MUAs) are required to provide the

MIME メイル利用者エージェントは次のものを提供する必要があります。

  • (a) the bodies of the MIME entities and the entity Content-* headers,
  • (b) the parameters of the Multipart/Related Content-type header, and
  • (c) the correspondence between each body's local file name, that body's header data, and, if present, the body part's content-ID.

5.2 6.2 Storing Multipart/Related Entities

The Multipart/Related media type will be used for objects that have internal linkages between the body parts. When the objects are stored the linkages may require processing by the application or its receiving agent.

multipart/related 媒体型は本体部分間の内部連結を持つ物体に使われます。 物体が蓄積される時に応用やその樹脂ねーじぇんとが連結を処理する必要があるかもしれません。

5.3 6.3 Recursion

MIME is a recursive structure. Hence one must expect a Multipart/Related entity to contain other Multipart/Related entities. When a Multipart/Related entity is being processed for display or storage, any enclosed Multipart/Related entities shall be processed as though they were being stored. It shall be the responsibility of the application handling the outermost Multipart/Related to insure the appropriate processing of embedded Multipart/Related entities.

MIME は再帰的構造です。ですから multipart/related 実体が別の multipart/related 実体を含んでいることを想定しなければなりません。 multipart/related 実体が表示や蓄積のため処理される時、 囲まれた multipart/related 実体は蓄積されているものであるかのように処理しなければなりません。

5.5 6.4 Configuration Considerations

It is suggested that MUAs that use configuration mechanisms, see [CFG] for an example, refer to Multipart/Related as Multipart/Related/<type>, were <type> is the value of the "type" parameter.

MUA は設定機構を使う場合 multipart/related を指すのに Multipart/Related/<type> (<type>type 引数の値) のようにすることを提案します。

6. 7. Security considerations

Security considerations relevant to Multipart/Related are identical to those of the underlying content-type.

multipart/related に関係する安全上の考慮点は使用する内容型と同じでうs。

7. 8. Acknowledgments

This proposal is the result of conversations the author has had with many people. In particular, similar work was described by Harald A. Alvestrand (early drafts of Multipart/Related), Dave Crocker (Multipart/Families), and Keith Moore (Multipart/References). In addition, James Clark, Charles Goldfarb, Gary Houston, Ned Freed, Ray Moody, and Don Stinchfield, provided both encouragement and invaluable help. The author, however, take full responsibility for all errors contained in this document.

8. 9. References

[822] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, UDEL, August 1982 August 1982, University of Delaware, RFC 822 STD 11, RFC 822, August 1982.

[CID] E. Levinson Levinson, E., and J. Clark, "Message/External-Body Content-ID Access Type", 12/26/1995, RFC 1873 December 1995, Levinson, E., "Message/External-Body Content-ID Access Type", February 1997, RFC 2111 Work in Progress.

[CFG] Borenstein, N., "A User Agent Configuration Mechanism For Multimedia Mail Format Information", RFC 1524, RFC 1524, Bellcore, September 23, 1993, RFC 1524.

[DISP] R. Troost, Troost, R., and S. Dorner, "Communicating Presentation Information in Internet Messages: The Content-Disposition Header", June 7, 1995, RFC 1806 RFC 1806, June 1995.

[MIME] Borenstein, N., and and N. Freed Freed, N., "MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies", RFC 1521, Bellcore, Innosoft, September 1993 June 1992, RFC 1341 "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996.

9. Author's Address

   Edward Levinson
   Accurate Information Systems, Inc.
   2 Industrial Way
   Eatontown, NJ  07724-2265
   XIson, Inc.
   47 Clive Street
   Metuchen, NJ  08840-1060
   Phone: +1 908 389 5550
   +1 908 549 3716
   Phone: +1 908 494 1606
   EMail: ELevinson@Accurate.com
   EMail: XIson@cnj.digex.com

10. Changes from previous draft (RFC 2112)

Corrected cid urls to conform to RFC 2111; the angle brackets were removed.


[1] 第2版 (RFC 2112) は編集上のおかしな点 (謎の空白とか、 参考文献が第1版が参照しているものより古い版に戻っているとか) が多々あります。多くは第3版 (RFC 2387) で修正されていますが、 直っていない点 (参考文献の章の番号) もあります。