Network Working Group T. Howes
Request for Comments: 2425 M. Smith
Category: Standards Track Netscape Communications Corp.
F. Dawson
Lotus Development Corporation
September 1998
A MIME Content-Type for Directory Information
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 (1998). All Rights Reserved.
1. Abstract
This document defines a MIME Content-Type for holding directory
information. The definition is independent of any particular
directory service or protocol. The text/directory Content-Type is
defined for holding a variety of directory information, for example,
name, or email address, or logo. The text/directory Content-Type can
also be used as the root body part in a multipart/related Content-
Type for handling more complicated situations, especially those in
which non-textual information that already has a natural MIME
representation, for example, a photograph or sound, is to be
represented.
The text/directory Content-Type defines a general framework and
format for holding directory information in a simple "type:value"
form. We refer to "type" in this context meaning a property or
attribute with which the value is associated. Mechanisms are defined
to specify alternate languages, encodings and other meta-information.
This document also defines the procedure by which particular formats,
called profiles, for carrying application-specific information within
a text/directory Content-Type can be defined and registered, and the
conventions such formats must follow. It is expected that other
documents will be produced that define such formats for various
applications (e.g., white pages).
Howes, et. al. Standards Track [Page 1]RFC 2425 MIME Content-Type for Directory Information September 1998
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 [RFC-2119].
2. Table of Contents
Status of the Memo................................................ 1
Copyright Notice.................................................. 1
1. Abstract...................................................... 1
2. Table of Contents............................................. 2
3. Need for a MIME Directory Type................................ 3
4. Overview...................................................... 4
5. The text/directory Content-Type............................... 4
5.1. MIME media type name........................................ 4
5.2. MIME subtype name........................................... 5
5.3. Required parameters......................................... 5
5.4. Optional parameters......................................... 5
5.5. Encoding considerations..................................... 5
5.6. Security considerations..................................... 6
5.7. Interoperability considerations............................. 6
5.8. Published specification..................................... 6
5.8.1. Line delimiting and folding............................... 6
5.8.2. ABNF content-type definition.............................. 7
5.8.3. Pre-defined Parameters.................................... 9
5.8.4. Pre-defined Value Types...................................11
5.9. Applications which use this media type......................14
5.10. Additional information.....................................14
5.11. Person & email address to contact for further information..14
5.12. Intended usage.............................................14
5.13. Author/Change controller...................................15
6. Predefined Types..............................................15
6.1. SOURCE Type Definition......................................15
6.2. NAME Type Definition........................................16
6.3. PROFILE Type Definition.....................................16
6.4. BEGIN Type Definition.......................................17
6.5. END Type Definition.........................................17
7. Use of the multipart/related Content-Type.....................18
8. Examples.......................................................18
8.1. Example 1...................................................19
8.2. Example 2...................................................19
8.3. Example 3...................................................20
8.4. Example 4...................................................21
9. Registration of new profiles..................................22
9.1. Define the profile..........................................22
9.2. Post the profile definition.................................23
9.3. Allow a comment period......................................23
9.4. Submit the profile for approval.............................23
10. Profile Change Control.......................................23
Howes, et. al. Standards Track [Page 2]
RFC 2425 MIME Content-Type for Directory Information September 1998
11. Registration of new types....................................24
11.1. Define the type............................................24
11.2. Post the type definition...................................25
11.3. Allow a comment period.....................................25
11.4. Submit the type for approval...............................25
12. Type Change Control..........................................25
13. Registration of new parameters...............................26
13.1. Define the parameter.......................................26
13.2. Post the parameter definition..............................27
13.3. Allow a comment period.....................................27
13.4. Submit the parameter for approval..........................27
14. Parameter Change Control.....................................28
15. Registration of new value types..............................28
15.1. Define the value type......................................28
15.2. Post the value type definition.............................29
15.3. Allow a comment period.....................................29
15.4. Submit the value type for approval.........................29
16. Security Considerations......................................30
17. Acknowledgements..............................................30
18. References....................................................30
19. Authors' Addresses...........................................32
20. Full Copyright Statement......................................33
3. Need for a MIME Directory Type
For purposes of this document, a directory is a special-purpose
database that contains typed information. A directory usually
supports both read and search of the information it contains, and can
support creation and modification of the information as well.
Directory information is usually accessed far more often than it is
updated. Directories can be local or global in scope. They can be
distributed or centralized. The information they contain can be
replicated, with weak or strong consistency requirements.
There are several situations in which users of Internet mail might
wish to exchange directory information: the email analogy of a
"business card" exchange; the conveyance of directory information to
a user having only email access to the Internet; the provision of
machine-parseable address information when purchasing goods or
services over the Internet; etc. As MIME [RFC-2045, RFC-2046] is
used increasingly by other protocols, most notably HTTP, it can also
be useful for these protocols to carry directory information in MIME
format. Such a format, for example, could be used to represent URC
(uniform resource characteristics) information about resources on the
World Wide Web, or to provide a rudimentary directory service over
HTTP.
Howes, et. al. Standards Track [Page 3]
RFC 2425 MIME Content-Type for Directory Information September 1998
4. Overview
The scheme defined here for representing directory information in a
MIME Content-Type has two parts. First, the text/directory Content-
Type is defined for use in holding directory information within a
single body part, for example name, title, or email address. In its
simplest form, the format uses a "type:value" approach, which should
be easily parseable by existing MIME implementations and
understandable by users. More complicated situations can be
represented also. This document defines the general form the
information in the Content-Type should have, and the procedure by
which specific types and values (properties) for particular
applications can be defined. The framework is general enough to
handle information from any number of end directory services,
including LDAP [RFC-1777, RFC-1778], WHOIS++ [RFC-1835], and X.500
[X500].
Directory entries can include far more than just textual information.
Some such information (e.g., an image or sound) overlaps with
predefined MIME Content-Types. In these cases it can be desirable to
include the information in its well-known MIME format. This situation
is handled by using a multipart/related Content-Type as defined in
[RFC-2112]. The root component of this type is a text/directory body
part specifying any in-line information, and for information
contained in other Content-Types, the Content-IDs (in URI form) of
those parts.
In some applications, it can be useful to include a pointer (e.g, a
URI) to some directory information rather than the information
itself. This document defines a general mechanism for accomplishing
this.
5. The text/directory Content-Type
The text/directory Content-Type is used to hold basic directory
information and URIs referencing other information, including other
MIME body parts holding supplementary or non-textual directory
information, such as an image or sound. It is defined as follows,
using the MIME media type registration template from [RFC-2048].
To: ietf-types@uninett.no
Subject: Registration of MIME media type text/directory
5.1. MIME media type name
MIME media type name: text
Howes, et. al. Standards Track [Page 4]
RFC 2425 MIME Content-Type for Directory Information September 1998
5.2. MIME subtype name
MIME subtype name: directory
5.3. Required parameters
Required parameters: charset
The "charset" parameter is as defined in [RFC-2046] for other body
parts. It is used to identify the default character set used within
the body part.
5.4. Optional parameters
Optional parameters: profile
The "profile" parameter is used to convey the type(s) of entity(ies)
to which the directory information pertains and the likely set of
information associated with the entity(ies). It is intended only as a
guide to applications interpreting the information contained within
the body part. It SHOULD NOT be used to exclude or require particular
pieces of information unless a profile definition specifically calls
for this behavior. Unless specifically forbidden by a particular
profile definition, a text/directory content type can contain
arbitrary attribute/value pairs.
The value of the "profile" parameter is defined as follows. Profile
names are case insensitive (i.e., the profile name "vCard" is the
same as "VCARD" and "vcard" and "vcArD").
profile = x-name / iana-token
x-name = "x-" 1*(ALPHA / DIGIT / "-")
; Names beginning with "x-" or "X-" are
; reserved for experimental use not intended for released
; products, or for use in bilateral agreements.
iana-token = <a publicly-defined extension token, registered
with IANA, as specified in Section 9 of this
document>
5.5. Encoding considerations
The default encoding is 8bit. Otherwise, as specified by the
Content-Transfer-Encoding header field.
Howes, et. al. Standards Track [Page 5]RFC 2425 MIME Content-Type for Directory Information September 1998
5.6. Security considerations
Directory information can be public or it can be protected from
unauthorized access by the directory service in which it resides.
Once the information leaves its native service, there can be no
guarantee that the same care will be taken by all services handling
the information. Furthermore, this specification defines no access
control mechanism by which information can be protected, or by which
access control information can be conveyed. Note that the integrity
and privacy of a text/directory body part can be protected by
enclosing it within an appropriate MIME-based security mechanism.
5.7. Interoperability considerations
In order to make sense of directory information, applications must
share a common understanding of the types of information contained
within the Content-Type (the directory schema). This schema
information is not defined in this document, but rather in companion
documents (e.g., [MIME-VCARD]) that follow the requirements specified
in this document, or in bilateral agreements between communicating
parties.
5.8. Published specification
The text/directory Content-Type contains directory information,
typically pertaining to a single directory entity or group of
entities. The content consists of one or more lines in the format
given below.
5.8.1. Line delimiting and folding
Individual lines within the MIME text/directory Content Type body are
delimited by the [RFC-822] line break, which is a CRLF sequence
(ASCII decimal 13, followed by ASCII decimal 10). Long logical lines
of text can be split into a multiple-physical-line representation
using the following folding technique.
A logical line MAY be continued on the next physical line anywhere
between two characters by inserting a CRLF immediately followed by a
single white space character (space, ASCII decimal 32, or horizontal
tab, ASCII decimal 9). At least one character must be present on the
folded line. Any sequence of CRLF followed immediately by a single
white space character is ignored (removed) when processing the
content type. For example the line:
DESCRIPTION:This is a long description that exists on a long line.
Can be represented as:
Howes, et. al. Standards Track [Page 6]
RFC 2425 MIME Content-Type for Directory Information September 1998
DESCRIPTION:This is a long description
that exists on a long line.
It could also be represented as:
DESCRIPTION:This is a long descrip
tion that exists o
n a long line.
The process of moving from this folded multiple-line representation
of a type definition to its single line representation is called
unfolding. Unfolding is accomplished by regarding CRLF immediately
followed by a white space character (namely HTAB ASCII decimal 9 or
SPACE ASCII decimal 32) as equivalent to no characters at all (i.e.,
the CRLF and single white space character are removed).
5.8.2. ABNF content-type definition
The following ABNF uses the notation of RFC 2234, which also defines
CRLF, WSP, DQUOTE, VCHAR, ALPHA, and DIGIT. After the unfolding of
any folded lines as described above, the syntax for a line of this
content type is as follows:
contentline = [group "."] name *(";" param) ":" value CRLF
; When parsing a content line, folded lines MUST first
; be unfolded according to the unfolding procedure
; described above.
; When generating a content line, lines longer than 75
; characters SHOULD be folded according to the folding
; procedure described above.
group = 1*(ALPHA / DIGIT / "-")
name = x-name / iana-token
iana-token = 1*(ALPHA / DIGIT / "-")
; identifier registered with IANA
x-name = "x-" 1*(ALPHA / DIGIT / "-")
; Names that begin with "x-" or "X-" are
; reserved for experimental use, not intended for released
; products, or for use in bilateral agreements.
param = param-name "=" param-value *("," param-value)
param-name = x-name / iana-token
param-value = ptext / quoted-string
Howes, et. al. Standards Track [Page 7]RFC 2425 MIME Content-Type for Directory Information September 1998
ptext = *SAFE-CHAR
value = *VALUE-CHAR
/ valuespec ; valuespec defined in section 5.8.4
quoted-string = DQUOTE *QSAFE-CHAR DQUOTE
NON-ASCII = %x80-FF
; use restricted by charset parameter
; on outer MIME object (UTF-8 preferred)
QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-ASCII
; Any character except CTLs, DQUOTE
SAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E / NON-ASCII
; Any character except CTLs, DQUOTE, ";", ":", ","
VALUE-CHAR = WSP / VCHAR / NON-ASCII
; any textual character
A line that begins with a white space character is a continuation of
the previous line, as described above. The white space character and
immediately preceeding CRLF should be discarded when reconstructing
the original line. Note that this line-folding convention differs
from that found in RFC 822, in that the sequence <CRLF><WSP> found
anywhere in the content indicates a continued line and should be
removed.
Various type names and the format of the corresponding values are
defined as specified in Section 11. Specifications MAY impose
ordering on the type constructs within a body part, though none is
required by default. The various x-name constructs are used for
bilaterally-agreed upon type names, parameter names and parameter
values, or for use in experimental settings.
Type names and parameter names are case insensitive (e.g., the type
name "fn" is the same as "FN" and "Fn"). Parameter values MAY be case
sensitive or case insensitive, depending on their definition.
The group construct is used to group related attributes together.
The group name is a syntactic convention used to indicate that all
type names prefaced with the same group name SHOULD be grouped
together when displayed by an application. It has no other
significance. Implementations that do not understand or support
grouping MAY simply strip off any text before a "." to the left of
the type name and present the types and values as normal.
Howes, et. al. Standards Track [Page 8]RFC 2425 MIME Content-Type for Directory Information September 1998
Each attribute defined in the text/directory body MAY have multiple
values, if allowed in the definition of the profile in which the
attribute is used. The general rule for encoding multi-valued items
is to simply create a new content line for each value (including the
type name). However, it should be noted that some value types
support encoding multiple values in a single content line by
separating the values with a comma ",". This approach has been taken
for several of the content types defined below (date, time, integer,
float), for space-saving reasons.
5.8.3. Pre-defined Parameters
The following parameters and value types are defined for general use.
predefined-param = encodingparm
/ valuetypeparm
/ languageparm
/ contextparm
encodingparm = "encoding" "=" encodingtype
encodingtype = "b" ; from RFC 2047
/ iana-token ; registered as described in
; section 15 of this document
valuetypeparm = "value" "=" valuetype
valuetype = "uri" ; genericurl from secion 5 of RFC 1738
/ "text"
/ "date"
/ "time"
/ "date-time" ; date time
/ "integer"
/ "boolean"
/ "float"
/ x-name
/ iana-token ; registered as described in
; section 15 of this document
languageparm = "language" "=" Language-Tag
; Language-Tag is defined in section 2 of RFC 1766
contextparm = "context" "=" context
context = x-name
/ iana-token
Howes, et. al. Standards Track [Page 9]RFC 2425 MIME Content-Type for Directory Information September 1998
The "language" type parameter is used to identify data in multiple
languages. There is no concept of "default" language, except as
specified by any "Content-Language" MIME header parameter that is
present. The value of the "language" type parameter is a language
tag as defined in Section 2 of [RFC-1766].
The "context" type parameter is used to identify a context (e.g., a
protocol) used in interpreting the value. This is used, for example,
in the "source" type, defined below.
The "encoding" type parameter is used to specify an alternate
encoding for a value. If the value contains a CRLF, it must be
encoded, since CRLF is used to separate lines in the content-type
itself. Currently, only the "b" encoding is supported.
The "b" encoding can also be useful for binary values that are mixed
with other text information in the body part (e.g., a certificate).
Using a per-value "b" encoding in this case leaves the other
information in a more readable form. The encoded base 64 value can be
split across multiple physical lines in the content type by using the
line folding technique described above.
The Content-Transfer-Encoding header field is used to specify the
encoding used for the body part as a whole. The "encoding" type
parameter is used to specify an encoding for a particular value
(e.g., a certificate). In this case, the Content-Transfer-Encoding
header might specify "8bit", while the one certificate value might
specify an encoding of "b" via an "encoding=b" type parameter.
The Content-Transfer-Encoding and the encodings of individual types
given by the "encoding" type parameter are independent of one
another. When encoding a text/directory body part for transmission,
individual type encodings are performed first, then the entire body
part is encoded according to the Content-Transfer-Encoding. When
decoding a text/directory body part, the Content-Transfer-Encoding is
decoded first, and then any individual types with an "encoding" type
parameter are decoded.
The "value" parameter is optional, and is used to identify the value
type (data type) and format of the value. The use of these
predefined formats is encouraged even if the value parameter is not
explicity used. By defining a standard set of value types and their
formats, existing parsing and processing code can be leveraged.
Including the value type explicitly as part of each property provides
an extra hint to keep parsing simple and support more generalized
applications. For example a search engine would not have to know the
particular value types for all of the items for which it is
Howes, et. al. Standards Track [Page 10]
RFC 2425 MIME Content-Type for Directory Information September 1998
searching. Because the value type is explicit in the definition, the
search engine could look for dates in any item type and provide
results that can still be interpreted.
5.8.4. Pre-defined Value Types
The format for values corresponding to the predefined valuetype
specifications given above are defined.
valuespec = text-list
/ genericurl ; from section 5 of RFC 1738
/ date-list
/ time-list
/ date-time-list
/ boolean
/ integer-list
/ float-list
/ iana-valuespec
text-list = *TEXT-LIST-CHAR *("," *TEXT-LIST-CHAR)
TEXT-LIST-CHAR = "\\" / "\," / "\n"
/ <any VALUE-CHAR except , or \ or newline>
; Backslashes, newlines, and commas must be encoded.
; \n or \N can be used to encode a newline.
date-list = date *("," date)
time-list = time *("," time)
date-time-list = date "T" time *("," date "T" time)
boolean = "TRUE" / "FALSE"
integer-list = integer *("," integer)
integer = [sign] 1*DIGIT
float-list = float *("," float)
float = [sign] 1*DIGIT ["." 1*DIGIT]
sign = "+" / "-"
date = date-fullyear ["-"] date-month ["-"] date-mday
date-fullyear = 4 DIGIT
Howes, et. al. Standards Track [Page 11]RFC 2425 MIME Content-Type for Directory Information September 1998
date-month = 2 DIGIT ;01-12
date-mday = 2 DIGIT ;01-28, 01-29, 01-30, 01-31
;based on month/year
time = time-hour [":"] time-minute [":"] time-second [time-secfrac]
[time-zone]
time-hour = 2 DIGIT ;00-23
time-minute = 2 DIGIT ;00-59
time-second = 2 DIGIT ;00-60 (leap second)
time-secfrac = "," 1*DIGIT
time-zone = "Z" / time-numzone
time-numzome = sign time-hour [":"] time-minute
iana-valuespec = <a publicly-defined valuetype format, registered
with IANA, as defined in section 15 of this
document>
Some specific notes on the value types and formats:
"text": The "text" value type should be used to identify values that
contain human-readable text. The character set and language in which
the text is represented is controlled by the charset content-header
and the language type parameter and content-header.
Examples for "text":
this is a text value
this is one value,this is another
this is a single value\, with a comma encoded
A formatted text line break in a text value type MUST be represented
as the character sequence backslash (ASCII decimal 92) followed by a
Latin small letter n (ASCII decimal 110) or a Latin capital letter N
(ASCII decimal 78), that is "\n" or "\N".
For example a multiple line DESCRIPTION value of:
Mythical Manager
Hyjinx Software Division
BabsCo, Inc.
could be represented as:
Howes, et. al. Standards Track [Page 12]RFC 2425 MIME Content-Type for Directory Information September 1998
DESCRIPTION:Mythical Manager\nHyjinx Software Division\n
BabsCo\, Inc.\n
demonstrating the \n literal formatted line break technique, the
CRLF-followed-by-space line folding technique, and the backslash
escape technique.
"uri": The "uri" value type should be used to identify values that
are referenced by a URI (including a Content-ID URI), instead of
encoded in-line. These value references might be used if the value is
too large, or otherwise undesirable to include directly. The format
for the URI is as defined in RFC 1738.
Examples for "uri":
http://www.foobar.com/my/picture.jpg
ldap://ldap.foobar.com/cn=babs%20jensen
"date", "time", and "date-time": Each of these value types is based
on a subset of the definitions in ISO 8601 standard. Profiles MAY
place further restrictions on "date" and "time" values. Multiple
"date" and "time" values can be specified using the comma-separated
notation, unless restricted by a profile.
Examples for "date":
1985-04-12
1996-08-05,1996-11-11
19850412
Examples for "time":
10:22:00
102200
10:22:00.33
10:22:00.33Z
10:22:33,11:22:00
10:22:00-08:00
Examples for "date-time":
1996-10-22T14:00:00Z
1996-08-11T12:34:56Z
19960811T123456Z
1996-10-22T14:00:00Z,1996-08-11T12:34:56Z
"boolean": The "boolean" value type is used to express boolen values.
These values are case insensitive.
Examples: TRUE
false
True
Howes, et. al. Standards Track [Page 13]RFC 2425 MIME Content-Type for Directory Information September 1998
"integer": The "integer" value type is used to express signed
integers in decimal format. If sign is not specified, the value is
assumed positive "+". Multiple "integer" values can be specified
using the comma-separated notation, unless restricted by a profile.
Examples: 1234567890
-1234556790
+1234556790,432109876
"float": The "float" value type is used to express real numbers. If
sign is not specified, the value is assumed positive "+". Multiple
"float" values can be specified using the comma-separated notation,
unless restricted by a profile.
Examples: 20.30
1000000.0000001
1.333,3.14
5.9. Applications which use this media type
Applications which use this media type: Various
5.10. Additional information
Additional information: None
5.11. Person & email address to contact for further information
Tim Howes
Netscape Communications Corp.
501 East Middlefield Rd.
Mountain View, CA 94041
USA
howes@netscape.com
+1 415 937 3419
5.12. Intended usage
Intended usage: COMMON
Howes, et. al. Standards Track [Page 14]RFC 2425 MIME Content-Type for Directory Information September 1998
5.13. Author/Change controller
Tim Howes
Netscape Communications Corp.
501 East Middlefield Rd.
Mountain View, CA 94041
USA
howes@netscape.com
+1 415 937 3419
Mark Smith
Netscape Communications Corp.
501 East Middlefield Rd.
Mountain View, CA 94041
USA
mcs@netscape.com
+1 415 937 3477
Frank Dawson
Lotus Development Corporation
6544 Battleford Drive
Raleigh, NC 27613-3502
USA
frank_dawson@lotus.com
+1-919-676-9515
6. Predefined Types
The following types are generally useful regardless of the profile
being carried and are defined below using the text/directory MIME
type registration template defined in Section 11.1 of this document.
These types MAY be included in any profile, unless explicitly
forbidden in the profile definition.
6.1. SOURCE Type Definition
To: ietf-mime-direct@imc.org
Subject: Registration of text/directory MIME type SOURCE
Type name: SOURCE
Type purpose: To identify the source of directory information
contained in the content type.
Type encoding: 8bit
Type valuetype: uri
Howes, et. al. Standards Track [Page 15]
RFC 2425 MIME Content-Type for Directory Information September 1998
Type special notes: The SOURCE type is used to provide the means by
which applications knowledgable in the given directory service
protocol can obtain additional or more up-to-date information from
the directory service. It contains a URI as defined in [RFC-1738]
and/or other information referencing the directory entity or entities
to which the information pertains. When directory information is
available from more than one source, the sending entity can pick what
it considers to be the best source, or multiple SOURCE types can be
included. The interpretation of the value for a SOURCE type can
depend on the setting of the CONTEXT type parameter. The value of the
CONTEXT type parameter MUST be compatible with the value of the uri
prefix.
Type example:
SOURCE;CONTEXT=LDAP:ldap://ldap.host/cn=Babs%20Jensen,
%20o=Babsco,%20c=US
6.2. NAME Type Definition
To: ietf-mime-direct@imc.org
Subject: Registration of text/directory MIME type NAME
Type name: NAME
Type purpose: To identify the displayable name of the directory
entity to which information in the content type pertains.
Type encoding: 8bit
Type valuetype: text
Type special notes: The NAME type is used to convey the display name
of the entity to which the directory information pertains.
Type example:
NAME:Babs Jensen's Contact Information
6.3. PROFILE Type Definition
To: ietf-mime-direct@imc.org
Subject: Registration of text/directory MIME type PROFILE
Type name: PROFILE
Type purpose: To identify the type of directory entity to which
information in the content type pertains.
Type encoding: 8bit
Howes, et. al. Standards Track [Page 16]RFC 2425 MIME Content-Type for Directory Information September 1998
Type valuetype: A profile name, registered as described in Section 9
of this document or bilaterally agreed upon as described in Section
5.
Type special notes: The PROFILE type is used to convey the type of
the entity to which the directory information in the rest of the body
part pertains. It should be the same as the "profile" header
parameter, if present.
Type example:
PROFILE:vCard
6.4. BEGIN Type Definition
To: ietf-mime-direct@imc.org
Subject: Registration of text/directory MIME type BEGIN
Type name: BEGIN
Type purpose: To denote the beginning of a syntactic entity within a
text/directory content-type.
Type encoding: 8bit
Type valuetype: text, containing a profile name, registered as
described in Section 9 of this document or bilaterally-agreed upon as
described in Section 5.
Type special notes: The BEGIN type is used in conjunction with the
END type to delimit a profile containing a related set of properties
within an text/directory content-type. This construct can be used
instead of or in addition to wrapping separate sets of information
inside additional MIME headers. It is provided for applications that
wish to define content that can contain multiple entities within the
same text/directory content-type or to define content that can be
identifiable outside of a MIME environment.
Type example:
BEGIN:VCARD
6.5. END Type Definition
To: ietf-mime-direct@imc.org
Subject: Registration of text/directory MIME type END
Type name: END
Howes, et. al. Standards Track [Page 17]RFC 2425 MIME Content-Type for Directory Information September 1998
Type purpose: To denote the end of a syntactic entity within a
text/directory content-type.
Type encoding: 8bit
Type valuetype: text, containing a profile name, registered as
described in Section 9 of this document or bilaterally-agreed upon as
described in Section 5.
Type special notes: The END type is used in conjunction with the
BEGIN type to delimit a profile containing a related set of
properties within an text/directory content-type. This construct can
be used instead of or in addition to wrapping separate sets of
information inside additional MIME headers. It is provided for
applications that wish to define content that can contain multiple
entities within the same text/directory content-type or to define
content that can be identifiable outside of a MIME environment.
Type example:
END: VCARD
7. Use of the multipart/related Content-Type
The multipart/related Content-Type can be used to hold directory
information comprised of both text and non-text information or
directory information that already has a natural MIME representation.
The root body part within the multipart/related body part is
specified as defined in [RFC-2112] by a "start" parameter, or it is
the first body part in the absence of such a parameter. The root
body part must have a Content-Type of "text/directory". This part
holds inline information and makes reference to subsequent body parts
holding additional text or non-text directory information via their
Content-ID URIs as explained in Section 5.
The body parts referred to do not have to be in any particular order,
except as noted above for the root body part.
8. Examples
The following examples are for illustrative purposes only and are not
part of the definition.
Howes, et. al. Standards Track [Page 18]RFC 2425 MIME Content-Type for Directory Information September 1998
8.1. Example 1
The first example illustrates simple use of the text/directory
Content-Type. Note that no "profile" parameter is given, so an
application may not know what kind of directory entity the
information applies to. Note also the use of both hypothetical
official and bilaterally agreed upon types.
From: Whomever@wherever.com
To: Someone@somewhere.com
Subject: whatever
MIME-Version: 1.0
Message-ID: <id1@host.net>
Content-Type: text/directory
Content-ID: <id2@host.com>
cn:Babs Jensen
cn:Barbara J Jensen
sn:Jensen
email:babs@umich.edu
phone:+1 313 747-4454
x-id:1234567890
8.2. Example 2
The next example illustrates the use of the Quoted-Printable transfer
encoding defined in [RFC 2045] to include non-ASCII character in some
of the information returned, and the use of the optional "name" and
"source" types. It also illustrates the use of an "encoding" type
parameter to encode a certificate value in "b". A "vCard" profile
[MIME- VCARD] is used for the example.
Content-Type: text/directory;
charset="iso-8859-1";
profile="vCard"
Content-ID: <id3@host.com>
Content-Transfer-Encoding: Quoted-Printable
begin:VCARD
source:ldap://cn=bjorn%20Jensen, o=university%20of%20Michigan, c=US
name:Bjorn Jensen
fn:Bj=F8rn Jensen
n:Jensen;Bj=F8rn
email;type=internet:bjorn@umich.edu
tel;type=work,voice,msg:+1 313 747-4454
key;type=x509;encoding=B:dGhpcyBjb3VsZCBiZSAKbXkgY2VydGlmaWNhdGUK
end:VCARD
Howes, et. al. Standards Track [Page 19]RFC 2425 MIME Content-Type for Directory Information September 1998
8.3. Example 3
The next example illustrates the use of multi-valued type parameters,
the "language" type parameter, the "value" type parameter, folding of
long lines, the \n encoding for formatted lines, attribute grouping,
and the inline "b" encoding. A "vCard" profile [MIME-VCARD] is used
for the example.
Content-Type: text/directory; profile="vcard"; charset=iso-8859-1
Content-ID: <id3@host.com>
Content-Transfer-Encoding: Quoted-Printable
begin:vcard
source:ldap://cn=Meister%20Berger,o=Universitaet%20Goerlitz,c=DE
name:Meister Berger
fn:Meister Berger
n:Berger;Meister
bday;value=date:1963-09-21
o:Universit=E6t G=F6rlitz
title:Mayor
title;language=de;value=text:Burgermeister
note:The Mayor of the great city of
Goerlitz in the great country of Germany.
email;internet:mb@goerlitz.de
home.tel;type=fax,voice,msg:+49 3581 123456
home.label:Hufenshlagel 1234\n
02828 Goerlitz\n
Deutschland
key;type=X509;encoding=b:MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQ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end:vcard
Howes, et. al. Standards Track [Page 20]
RFC 2425 MIME Content-Type for Directory Information September 1998
8.4. Example 4
The final example illustrates the use of the multipart/related
Content-Type to include non-textual directory data via the "uri"
encoding to refer to other body parts within the same message, or to
external values. Note that no "profile" parameter is given, so an
application may not know what kind of directory entity the
information applies to. Note also the use of both hypothetical
official and bilaterally agreed upon types.
Content-Type: multipart/related;
boundary=woof;
type="text/directory";
start="<id5@host.com>"
Content-ID: <id4@host.com>
--woof
Content-Type: text/directory; charset="iso-8859-1"
Content-ID: <id5@host.com>
Content-Transfer-Encoding: Quoted-Printable
source:ldap://cn=Bjorn%20Jensen,o=University%20of%20Michigan,c=US
cn:Bj=F8rn Jensen
sn:Jensen
email:bjorn@umich.edu
image;value=uri:cid:id6@host.com
image;value=uri;format=jpeg:ftp://some.host/some/path.jpg
sound;value=uri:cid:id7@host.com
phone:+1 313 747-4454
--woof
Content-Type: image/jpeg
Content-ID: <id6@host.com>
<...image data...>
--woof
Content-Type: message/external-body;
name="myvoice.au";
site="myhost.com";
access-type=ANON-FTP;
directory="pub/myname";
mode="image"
Content-Type: audio/basic
Content-ID: <id7@host.com>
--woof--
Howes, et. al. Standards Track [Page 21]RFC 2425 MIME Content-Type for Directory Information September 1998
9. Registration of new profiles
This section defines procedures by which new profiles are registered
with the IANA and made available to the Internet community. Note that
non-IANA profiles can be used by bilateral agreement, provided the
associated profile names follow the "X-" convention defined above.
The procedures defined here are designed to allow public comment and
review of new profiles, while posing only a small impediment to the
definition of new profiles.
Registration of a new profile is accomplished by the following steps.
9.1. Define the profile
A profile is defined by completing the following template.
To: ietf-mime-direct@imc.org
Subject: Registration of text/directory MIME profile XXX
Profile name:
Profile purpose:
Profile types:
Profile special notes (optional):
Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
The explanation of what goes in each field in the template follows.
Profile name: The name of the profile as it will appear in the
text/directory MIME Content-Type "profile" header parameter, or the
predefined "profile" type name.
Profile purpose: The purpose of the profile (e.g., to represent
information about people, printers, documents, etc.). Give a short
but clear description.
Profile types: The list of types associated with the profile. This
list of types is to be expected but not required in the profile,
unless otherwise noted in the profile definition. Other types not
mentioned in the profile definition MAY also be present. Note that
any new types referenced by the profile MUST be defined separately as
described in Section 10.
Howes, et. al. Standards Track [Page 22]RFC 2425 MIME Content-Type for Directory Information September 1998
Profile special notes: Any special notes about the profile, how it is
to be used, etc. This section of the template can also be used to
define an ordering on the types that appear in the Content-Type, if
such an ordering is required.
9.2. Post the profile definition
The profile description must be posted to the new profile discussion
list, ietf-mime-direct@imc.org
9.3. Allow a comment period
Discussion on the new profile must be allowed to take place on the
list for a minimum of two weeks. Consensus must be reached on the
profile before proceeding to step 4.
9.4. Submit the profile for approval
Once the two-week comment period has elapsed, and the proposer is
convinced consensus has been reached on the profile, the registration
application should be submitted to the Profile Reviewer for approval.
The Profile Reviewer is appointed by the Application Area Directors
and can either accept or reject the profile registration. An accepted
registration is passed on by the Profile Reviewer to the IANA for
inclusion in the official IANA profile registry. The registration may
be rejected for any of the following reasons. 1) Insufficient comment
period; 2) Consensus not reached; 3) Technical deficiencies raised on
the list or elsewhere have not been addressed. The Profile Reviewer's
decision to reject a profile can be appealed by the proposer to the
IESG, or the objections raised can be addressed by the proposer and
the profile resubmitted.
10. Profile Change Control
Existing profiles can be changed using the same process by which they
were registered.
Define the change
Post the change
Allow a comment period
Submit the changed profile for approval
Howes, et. al. Standards Track [Page 23]RFC 2425 MIME Content-Type for Directory Information September 1998
Note that the original author or any other interested party can
propose a change to an existing profile, but that such changes should
only be proposed when there are serious omissions or errors in the
published specification. The Profile Reviewer can object to a change
if it is not backwards compatible, but is not required to do so.
Profile definitions can never be deleted from the IANA registry, but
profiles which are no longer believed to be useful can be declared
OBSOLETE by a change to their "intended use" field.
11. Registration of new types
This section defines procedures by which new types are registered
with the IANA. Note that non-IANA types can be used by bilateral
agreement, provided the associated types names follow the "X-"
convention defined above.
The procedures defined here are designed to allow public comment and
review of new types, while posing only a small impediment to the
definition of new types.
Registration of a new type is accomplished by the following steps.
11.1. Define the type
A type is defined by completing the following template.
To: ietf-mime-direct@imc.org
Subject: Registration of text/directory MIME type XXX
Type name:
Type purpose:
Type encoding:
Type valuetype:
Type special notes (optional):
Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
The meaning of each field in the template is as follows.
Type name: The name of the type, as it will appear in the body of an
text/directory MIME Content-Type "type: value" line to the left of
the colon ":".
Howes, et. al. Standards Track [Page 24]RFC 2425 MIME Content-Type for Directory Information September 1998
Type purpose: The purpose of the type (e.g., to represent a name,
postal address, IP address, etc.). Give a short but clear
description.
Type encoding: The default encoding a value of the type must have in
the body of a text/directory MIME Content-Type.
Type valuetype: The format a value of the type must have in the body
of a text/directory MIME Content-Type. This description must be
precise and must not violate the general encoding rules defined in
section 5 of this document.
Type special notes: Any special notes about the type, how it is to be
used, etc.
11.2. Post the type definition
The type description must be posted to the new type discussion list,
ietf-mime-direct@imc.org
11.3. Allow a comment period
Discussion on the new type must be allowed to take place on the list
for a minimum of two weeks. Consensus must be reached on the type
before proceeding to step 4.
11.4. Submit the type for approval
Once the two-week comment period has elapsed, and the proposer is
convinced consensus has been reached on the type, the registration
application should be submitted to the Profile Reviewer for approval.
The Profile Reviewer is appointed by the Application Area Directors
and can either accept or reject the type registration. An accepted
registration is passed on by the Profile Reviewer to the IANA for
inclusion in the official IANA profile registry. The registration can
be rejected for any of the following reasons. 1) Insufficient comment
period; 2) Consensus not reached; 3) Technical deficiencies raised on
the list or elsewhere have not been addressed. The Profile
Reviewer's decision to reject a type can be appealed by the proposer
to the IESG, or the objections raised can be addressed by the
proposer and the type resubmitted.
Howes, et. al. Standards Track [Page 25]
RFC 2425 MIME Content-Type for Directory Information September 1998
12. Type Change Control
Existing types can be changed using the same process by which they
were registered.
Define the change
Post the change
Allow a comment period
Submit the type for approval
Note that the original author or any other interested party can
propose a change to an existing type, but that such changes should
only be proposed when there are serious omissions or errors in the
published specification. The Profile Reviewer can object to a change
if it is not backwards compatible, but is not required to do so.
Type definitions can never be deleted from the IANA registry, but
types which are nolonger believed to be useful can be declared
OBSOLETE by a change to their "intended use" field.
13. Registration of new parameters
This section defines procedures by which new parameters are
registered with the IANA and made available to the Internet
community. Note that non-IANA parameters can be used by bilateral
agreement, provided the associated parameters names follow the "X-"
convention defined above.
The procedures defined here are designed to allow public comment and
review of new parameters, while posing only a small impediment to the
definition of new parameters.
Registration of a new parameter is accomplished by the following
steps.
13.1. Define the parameter
A parameter is defined by completing the following template.
To: ietf-mime-direct@imc.org
Subject: Registration of text/directory MIME type parameter XXX
Parameter name:
Parameter purpose:
Howes, et. al. Standards Track [Page 26]RFC 2425 MIME Content-Type for Directory Information September 1998
Parameter values:
Parameter special notes (optional):
Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
The explanation of what goes in each field in the template follows.
Parameter name: The name of the parameter as it will appear in the
text/directory MIME Content-Type.
Parameter purpose: The purpose of the parameter (e.g., to represent
the format of an image, type of a phone number, etc.). Give a short
but clear description. If defining a general paramemter like "format"
or "type" keep in mind that other applications might wish to extend
its use.
Parameter values: The list or description of values associated with
the parameter.
Parameter special notes: Any special notes about the parameter, how
it is to be used, etc.
13.2. Post the parameter definition
The parameter description must be posted to the new parameter
discussion list, ietf-mime-direct@imc.org
13.3. Allow a comment period
Discussion on the new parameter must be allowed to take place on the
list for a minimum of two weeks. Consensus must be reached on the
parameter before proceeding to step 4.
13.4. Submit the parameter for approval
Once the two-week comment period has elapsed, and the proposer is
convinced consensus has been reached on the parameter, the
registration application should be submitted to the Profile Reviewer
for approval. The Profile Reviewer is appointed by the Application
Area Directors and can either accept or reject the parameter
registration. An accepted registration is passed on by the Profile
Reviewer to the IANA for inclusion in the official IANA parameter
registry. The registration can be rejected for any of the following
reasons. 1) Insufficient comment period; 2) Consensus not reached; 3)
Technical deficiencies raised on the list or elsewhere have not been
addressed. The Profile Reviewer's decision to reject a profile can be
appealed by the proposer to the IESG, or the objections raised can be
Howes, et. al. Standards Track [Page 27]RFC 2425 MIME Content-Type for Directory Information September 1998
addressed by the proposer and the parameter registration resubmitted.
14. Parameter Change Control
Existing parameters can be changed using the same process by which
they were registered.
Define the change
Post the change
Allow a comment period
Submit the parameter for approval
Note that the original author or any other interested party can
propose a change to an existing parameter, but that such changes
should only be proposed when there are serious omissions or errors in
the published specification. The Profile Reviewer can object to a
change if it is not backwards compatible, but is not required to do
so.
Parameter definitions can never be deleted from the IANA registry,
but parameters which are nolonger believed to be useful can be
declared OBSOLETE by a change to their "intended use" field.
15. Registration of new value types
This section defines procedures by which new value types are
registered with the IANA and made available to the Internet
community. Note that non-IANA value types can be used by bilateral
agreement, provided the associated value types names follow the "X-"
convention defined above.
The procedures defined here are designed to allow public comment and
review of new value types, while posing only a small impediment to
the definition of new value types.
Registration of a new value types is accomplished by the following
steps.
15.1. Define the value type
A value type is defined by completing the following template.
To: ietf-mime-direct@imc.org
Subject: Registration of text/directory MIME value type XXX
Howes, et. al. Standards Track [Page 28]RFC 2425 MIME Content-Type for Directory Information September 1998
value type name:
value type purpose:
value type format:
value type special notes (optional):
Intended usage: (one of COMMON, LIMITED USE or OBSOLETE)
The explanation of what goes in each field in the template follows.
value type name: The name of the value type as it will appear in the
text/directory MIME Content-Type.
value type purpose: The purpose of the value type. Give a short but
clear description.
value type format: The definition of the format for the value,
usually using ABNF grammar.
value type special notes: Any special notes about the value type, how
it is to be used, etc.
15.2. Post the value type definition
The value type description must be posted to the new value type
discussion list, ietf-mime-direct@imc.org
15.3. Allow a comment period
Discussion on the new value type must be allowed to take place on the
list for a minimum of two weeks. Consensus must be reached before
proceeding to step 4.
15.4. Submit the value type for approval
Once the two-week comment period has elapsed, and the proposer is
convinced consensus has been reached on the value type, the
registration application should be submitted to the Profile Reviewer
for approval. The Profile Reviewer is appointed by the Application
Area Directors and can either accept or reject the value type
registration. An accepted registration should be passed on by the
Profile Reviewer to the IANA for inclusion in the official IANA value
type registry. The registration can be rejected for any of the
following reasons. 1) Insufficient comment period; 2) Consensus not
reached; 3) Technical deficiencies raised on the list or elsewhere
have not been addressed. The Profile Reviewer's decision to reject a
Howes, et. al. Standards Track [Page 29]RFC 2425 MIME Content-Type for Directory Information September 1998
profile can be appealed by the proposer to the IESG, or the
objections raised can be addressed by the proposer and the value type
registration resubmitted.
16. Security Considerations
Internet mail is subject to many well known security attacks,
including monitoring, replay, and forgery. Care should be taken by
any directory service in allowing information to leave the scope of
the service itself, where any access controls can no longer be
guaranteed. Applications should also take care to display directory
data in a "safe" environment (e.g., PostScript-valued types).
17. Acknowledgements
The registration procedures defined here were shamelessly lifted from
the MIME registration RFC.
The many valuable comments contributed by members of the IETF ASID
working group are gratefully acknowledged, as are the contributions
of the Versit Consortium. Chris Newman was especially helpful in
navigating the intricacies of ABNF lore.
18. References
[RFC-1777] Yeong, W., Howes, T., and S. Kille, "Lightweight
Directory Access Protocol", RFC 1777, March 1995.
[RFC-1778] Howes, T., Kille, S., Yeong, W., and C. Robbins, "The
String Representation of Standard Attribute Syntaxes",
RFC 1778, March 1995.
[RFC-822] Crocker, D., "Standard for the Format of ARPA Internet
Text Messages", STD 11, RFC 822, August 1982.
[RFC-2045] Borenstein, N., and N. Freed, "Multipurpose Internet
Mail Extensions (MIME) Part One: Format of Internet
Message Bodies", RFC 2045, November 1996.
[RFC-2046] Moore, K., "Multipurpose Internet Mail Extensions (MIME)
Part Two: Media Types", RFC 2046, November 1996.
[RFC-2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose
Internet Mail Extensions (MIME) Part Four: Registration
Procedures", RFC 2048, November 1996.
[RFC-1766] Alvestrand, H., "Tags for the Identification of
Languages", RFC 1766, March 1995.
Howes, et. al. Standards Track [Page 30]RFC 2425 MIME Content-Type for Directory Information September 1998
[RFC-2112] Levinson, E., "The MIME Multipart/Related Content-type",
RFC 2112, March 1997.
[X500] "Information Processing Systems - Open Systems
Interconnection - The Directory: Overview of Concepts,
Models and Services", ISO/IEC JTC 1/SC21, International
Standard 9594-1, 1988.
[RFC-1835] Deutsch, P., Schoultz, R., Faltstrom, P., and C. Weider,
"Architecture of the WHOIS++ service", RFC 1835, August
1995.
[RFC-1738] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
Resource Locators (URL)", RFC 1738, December 1994.
[MIME-VCARD] Dawson, F., and T. Howes, "VCard MIME Directory
Profile", RFC 2426, September 1998.
[VCARD] Internet Mail Consortium, "vCard - The Electronic
Business Card", Version 2.1,
http://www.imc.com/pdi/vcard-21.txt, September, 1996.
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC-2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
Howes, et. al. Standards Track [Page 31]RFC 2425 MIME Content-Type for Directory Information September 1998
19. Authors' Addresses
Tim Howes
Netscape Communications Corp.
501 East Middlefield Rd.
Mountain View, CA 94041
USA
Phone: +1.415.937.3419
EMail: howes@netscape.com
Mark Smith
Netscape Communications Corp.
501 East Middlefield Rd.
Mountain View, CA 94041
USA
Phone: +1.415.937.3477
EMail: mcs@netscape.com
Frank Dawson
Lotus Development Corporation
6544 Battleford Drive
Raleigh, NC 27613
USA
Phone: +1-919-676-9515
EMail: frank_dawson@lotus.com
Howes, et. al. Standards Track [Page 32]
RFC 2425 MIME Content-Type for Directory Information September 1998
20. Full Copyright Statement
Copyright (C) The Internet Society (1998). 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.
Howes, et. al. Standards Track [Page 33]
