Media Type Specifications and
Registration Procedures
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Applications
RFCRequest for CommentsMIMEmedia typesI-DInternet-Draft
This document defines procedures for the specification and
registration of media types for use in MIME and other Internet
protocols.
The media type registration process was initially defined for registering media
types for use in the context of the asynchronous Internet
mail environment. In this mail environment there is a need to limit the number
of possible media types, to increase the likelihood of interoperability when the
capabilities of the remote mail system are not known. As media types are used
in new environments in which the proliferation of media types is not a hindrance
to interoperability, the original procedure proved excessively restrictive and had
to be generalized. This was initially done in , but
the procedure defined there was still part of the MIME document set. The media
type specification and registration procedure has now been moved to this separate
document, to make it clear that it is independent of MIME.
It may be desirable to restrict the use of media types to specific environments
or to prohibit their use in other environments. This revision attempts for the first
time to incorporate such restrictions into media type registrations in a systematic way.
See for additional discussion.
Recent Internet protocols have been carefully designed to be easily extensible
in certain areas. In particular, many protocols, including but not limited
to MIME, are capable of carrying arbitrary labeled
content. A mechanism is needed to label such content and
a registration process is needed for these labels,
to ensure that the set of such values is developed in an
orderly, well-specified, and public manner.
This document defines media type specification and registration procedures that use
the Internet Assigned Numbers Authority (IANA) as a central registry.
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 .
This specification makes use of the
Augmented Backus-Naur Form (ABNF) notation,
including the core rules defined in Appendix A of that document.
Registration of a new media type or types starts with the construction of a
registration proposal. Registration may occur within several different
registration trees that have different requirements, as discussed below. In
general, a new registration proposal is circulated and reviewed in a fashion
appropriate to the tree involved. The media type is then registered if the
proposal is acceptable. The following sections describe the requirements and
procedures used for each of the different registration trees.
In order to increase the efficiency and flexibility of the registration
process, different structures of subtype names may be registered to accommodate
the different natural requirements for, e.g., a subtype that will be
recommended for wide support and implementation by the Internet community, or a
subtype that is used to move files associated with proprietary software. The
following subsections define registration "trees" that are distinguished by the use of
faceted names, e.g., names of the form "tree.subtree...subtype". Note that
some media types defined prior to this document do not conform to the naming
conventions described below. See Appendix A for a discussion of them.
The standards tree is intended for types of general interest to the
Internet community. Registrations in the standards tree MUST be either:
approved directly by the IESG, or
registered using the "Specification Required"
IANA registration policy (which implies Expert Review).
The former procedure is used for registering registrations from IETF Consensus
documents, or in rare cases when registering a grandfathered (see
) and/or otherwise incomplete
registration is in the interest of the Internet community.
In the latter case the IESG makes the decision on whether the registration
submitter represents a recognized Standards Body; after that a
Media Types Reviewer (Designated Expert or a group of Designated Experts)
performs the expert review as specified in this document.
In the case of registration for the IETF itself, the registration
proposal MUST be published as an IETF Consensus RFC.
Registrations published in non-IETF RFC streams are allowed and
require IESG approval.
Standards-tree registration RFCs can either be standalone
"registration only" RFCs, or they can be incorporated into a more
general specification of some sort.
Media types in the standards tree are normally denoted by names that
are not explicitly faceted, i.e., do not contain period (".", full
stop) characters.
The "owner" of a media type registration in the standards tree is
assumed to be the standards body itself. Modification or alteration
of the specification requires the same level of processing (e.g.,
a registration submitted on Standards Track can be revised in another
Standards Track RFC, but can't be revised in an Informational RFC)
required for the initial registration.
The vendor tree is used for media types associated with commercially available
products. "Vendor" or "producer" are construed as equivalent and very broadly
in this context.
A registration may be placed in the vendor tree by anyone who needs to
interchange files associated with the particular product. However, the
registration formally belongs to the vendor or organization producing the
software or file format being registered. Changes to the specification will be made at their
request, as discussed in subsequent sections.
Registrations in the vendor tree will be distinguished by the leading facet
"vnd.". That may be followed, at the discretion of the registrant, by either
a media subtype name from a well-known producer (e.g., "vnd.mudpie") or by an
IANA-approved designation of the producer's name that is followed by a
media type or product designation (e.g., vnd.bigcompany.funnypictures).
While public exposure and review of media types to be registered in the vendor
tree is not required, using the ietf-types@iana.org mailing list for review is
strongly encouraged to improve the quality of those specifications. Registrations
in the vendor tree may be submitted directly to the IANA, where they will undergo
Expert Review prior to approval.
Registrations for media types created experimentally or as part of products
that are not distributed commercially may be registered in the personal or
vanity tree. The registrations are distinguished by the leading facet "prs.".
The owner of "personal" registrations and associated specifications is the
person or entity making the registration, or one to whom responsibility has
been transferred as described below.
While public exposure and review of media types to be registered in the
personal tree is not required, using the ietf-types list for review is strongly
encouraged to improve the quality of those specifications. Registrations in
the personal tree may be submitted directly to the IANA, where they will undergo
Expert Review prior to approval.
For convenience and symmetry with this registration scheme, subtype names
with "x." as the first facet may be used for the same purposes for which names
starting in "x-" are used. These types are unregistered,
experimental, and for use only with the active agreement of the parties
exchanging them.
However, with the simplified registration procedures described above for vendor
and personal trees, it should rarely, if ever, be necessary to use unregistered
experimental types. Therefore, use of both "x-" and "x." forms is discouraged.
Types in this tree MUST NOT be registered. If a generally useful and widely
deployed type incorrectly ends up with an "x." or "x-" name prefix, it
MAY be registered using its current name in an alternate tree by following the
procedure defined in .
From time to time and as required by the community, the IANA may,
by and with the advice and consent of the IESG, create new top-level registration
trees. It is explicitly assumed that these trees may be created for external
registration and management by well-known permanent bodies; for example, scientific
societies may register media types specific to the sciences they cover. In general,
the quality of review of specifications for one of these additional registration
trees is expected to be equivalent to registrations in the standards tree.
Establishment of these new trees MUST be done with a Standards Track RFC.
Media type registration proposals are all expected to conform to various
requirements laid out in the following sections. Note that requirement
specifics sometimes vary depending on the registration tree, again as detailed
in the following sections.
Media types MUST function as an actual media format. Registration of things
that are better thought of as a transfer encoding, as a charset, or as a
collection of separate entities of another type, is not allowed. For example,
although applications exist to decode the base64 transfer encoding
, base64 cannot be registered as a media type.
This requirement applies regardless of the registration tree involved.
All registered media types MUST be assigned type and subtype names. The
combination of these names serves to uniquely identify the media type,
and the format of the subtype name identifies the registration tree. Both
type and subtype names are case-insensitive.
Type and subtype names beginning with "X-" are reserved for experimental use
and MUST NOT be registered. This parallels
the restriction on the x. tree, as discussed in .
Type and subtype names MUST conform to the following ABNF:
Note that this syntax is somewhat more restrictive than what is allowed by
the ABNF in .
Although the name syntax treates "+" as equivalent to any other character,
it is used in media type names to introduce a structured syntax specificer
suffix. Structured syntax suffix requirements are specified in
.
While it is possible for a given media type to be assigned additional names,
the use of different names to identify the same media type is discouraged.
These requirements apply regardless of the registration tree involved.
The choice of top-level type name MUST take into account the nature of media type
involved. New subtypes of top-level types MUST conform to the restrictions
of the top-level type, if any. The following sections describe each of the
initial set of top-level types and their associated restrictions. Additionally,
various protocols, including but not limited to MIME, MAY impose additional
restrictions on the media types they can transport. (See
for additional information on the restrictions
MIME imposes.)
The "text" media type is intended for sending material that is principally
textual in form. A "charset" parameter MAY be used to indicate the charset
of the body text for "text" subtypes, notably including the subtype
"text/plain", which is a generic subtype for plain text defined in
. If defined, a text "charset" parameter MUST
be used to specify a charset name defined in accordance to the procedures
laid out in .
Plain text does not
provide for or allow formatting commands, font attribute specifications,
processing instructions, interpretation directives, or content markup. Plain
text is seen simply as a linear sequence of characters, possibly interrupted by
line breaks or page breaks. Plain text MAY allow the stacking of several
characters in the same position in the text. Plain text in scripts like Arabic
and Hebrew may also include facilities that allow the arbitrary mixing of text
segments with opposite writing directions.
Beyond plain text, there are many formats for representing what might be known
as "rich text". An interesting characteristic of many such representations is
that they are to some extent readable even without the software that interprets
them. It is useful to distinguish them, at the highest level, from such
unreadable data as images, audio, or text represented in an unreadable form.
In the absence of appropriate interpretation software, it is reasonable to present
subtypes of "text" to the user, while it is not reasonable to do so with most
non-textual data. Such formatted textual data should be represented using
subtypes of "text".
A media type of "image" indicates that the content specifies one or more separate images
that require appropriate hardware to display. The subtype names the specific image format.
A media type of "audio" indicates that the content contains audio data.
A media type of "video" indicates that the content specifies a time-varying-picture
image, possibly with color and coordinated sound. The term 'video' is used in
its most generic sense, rather than with reference to any particular technology
or format, and is not meant to preclude subtypes such as animated drawings
encoded compactly.
Note that although in general this document strongly discourages the mixing of
multiple media in a single body, it is recognized that many so-called video
formats include a representation for synchronized audio and/or text, and this is
explicitly permitted for subtypes of "video".
The "application" media type is to be used for discrete data that do not
fit in any of the media types, and particularly for data to be processed
by some type of application program. This is information that must be
processed by an application before it is viewable or usable by a user.
Expected uses for the "application" media type include but are not limited
to file transfer,
spreadsheets, presentations, scheduling data, and languages for
"active" (computational) material. (The latter, in particular, can pose
security problems that must be understood by implementors, and are considered
in detail in the discussion of the "application/PostScript" media type in
.)
For example, a meeting scheduler might define a standard representation for
information about proposed meeting dates. An intelligent user agent would use
this information to conduct a dialog with the user, and might then send
additional material based on that dialog. More generally, there have been
several "active" languages developed in which programs in a suitably
specialized language are transported to a remote location and automatically run
in the recipient's environment.
Such applications may be defined as subtypes of the "application" media type.
The subtype of "application" will often be either the name or include part of
the name of the application for which the data are intended. This does not
mean, however, that any application program name may be used freely as a
subtype of "application".
Multipart and message are composite types, that is, they provide a means
of encapsulating zero or more objects, each labeled with its own media type.
All subtypes of multipart and message MUST conform to the syntax rules
and other requirements specified in .
In some cases a new media type may not "fit" under any currently defined
top-level content type. Such cases are expected to be quite rare. However, if
such a case does arise a new top-level type can be defined to accommodate it. Such
a definition MUST be done via standards-track RFC; no other mechanism can be
used to define additional top-level content types.
defined the first such augmentation to the
media type definition to additionally specify the underlying structure
of that media type. To quote:
This document also standardizes a convention (using
the suffix '+xml') for naming media types ... when those
media types represent XML MIME (Multipurpose
Internet Mail Extensions) entities.
That is, it specified a suffix (in that case, +xml) to be
appended to the base media type name.
Since this was published, the defacto practice has arisen for using this
suffix convention for other well-known structuring syntaxes.
In particular, media types have been registered with suffixes
such as +der, +fastinfoset and +json. This specification formalizes this
practice and sets up a registry for structured type name suffixes.
The primary guideline for whether a structured type name suffix should be
registerable is that it be) described by a readily-available description, preferably
within a document published by an established standards organization, and for
which there's a reference that can be used in a References section of
an RFC.
Media types that make use of a named structured syntax SHOULD
use the appropriate registered +suffix for that structured syntax
when they are registered. By the same token, media types MUST NOT be given
names incorporating suffixes for structured syntaxes they do not actually
employ. "+suffix" constructs for as-yet unregistered structured syntaxes
should be used with care, given the possibility of conflicts with future
suffix definitions.
Media types MAY elect to use one or more media type parameters, or some
parameters may be automatically made available to the media type by virtue of
being a subtype of a content type that defines a set of parameters applicable
to any of its subtypes. In either case, the names, values, and meanings of any
parameters MUST be fully specified when a media type is registered in the standards
tree, and SHOULD be specified as completely as possible when media types are
registered in the vendor or personal trees.
Parameter names have the syntax as media type names and values:
Note that this syntax is somewhat more restrictive than what is allowed by the ABNF
in and amended by .
There is no defined syntax for parameter values. Therefore registrations MUST
specify parameter value syntax. Additionally, some transports impose restrictions
on parameter value syntax, so care should be taken to limit the use of potentially
problematic syntaxes; e.g., pure binary valued parameters, while permitted in some
protocols, probably should be avoided.
New parameters SHOULD NOT be defined as a way to introduce new functionality in
types registered in the standards tree, although new parameters MAY be added to
convey additional information that does not otherwise change existing
functionality. An example of this would be a "revision" parameter to indicate
a revision level of an external specification such as JPEG. Similar
behavior is encouraged for media types registered in the vendor
or personal trees but is not required.
All registered media types MUST employ a single, canonical data format,
regardless of registration tree.
A precise and openly available specification of the format of each media type
MUST exist for all types registered in the standards tree and MUST at a minimum be
referenced by, if it isn't actually included in, the media type registration
proposal itself.
The specifications of format and processing particulars may or may not be
publicly available for media types registered in the vendor tree, and such
registration proposals are explicitly permitted to limit specification to
which software and version produce or process such media types. References
to or inclusion of format specifications in registration proposals is
encouraged but not required.
Format specifications are still required for registration in the personal tree,
but may be either published as RFCs or otherwise deposited with the IANA.
The deposited specifications will meet the same criteria as those required to
register a well-known TCP port and, in particular, need not be made public.
Some media types involve the use of patented technology. The registration of
media types involving patented technology is specifically permitted. However,
the restrictions set forth in on the use
of patented technology in IETF
standards-track protocols must be respected when the specification of a media
type is part of a standards-track protocol. In addition, other standards bodies
making use of the standards tree may have their own rules regarding intellectual
property that must be observed in their registrations.
Media types SHOULD interoperate across as many systems and
applications as possible. However, some media types will inevitably have
problems interoperating across different platforms. Problems with different
versions, byte ordering, and specifics of gateway handling can and will arise.
Universal interoperability of media types is not required, but known
interoperability issues SHOULD be identified whenever possible. Publication of
a media type does not require an exhaustive review of interoperability, and
the interoperability considerations section is subject to continuing
evaluation.
These recommendations apply regardless of the registration tree involved.
An analysis of security issues MUST be done for all types registered
in the standards Tree. A similar analysis for media types registered in the
vendor or personal trees is encouraged but not required. However, regardless
of what security analysis has or has not been done, all descriptions of
security issues MUST be as accurate as possible regardless of registration
tree. In particular, a statement that there are "no security issues
associated with this type" MUST NOT be confused with "the security issues
associates with this type have not been assessed".
There is absolutely no requirement that media types registered in any tree be
secure or completely free from risks. Nevertheless, all known security risks
MUST be identified in the registration of a media type, again regardless of
registration tree.
The security considerations section of all registrations is subject to
continuing evaluation and modification, and in particular MAY be extended by
use of the "comments on media types" mechanism described in
below.
Some of the issues that should be looked at in a security analysis of a media
type are:
Complex media types may include provisions for directives that institute
actions on a recipient's files or other resources. In many cases provision is
made for originators to specify arbitrary actions in an unrestricted fashion
that may then have devastating effects. See the registration of the
application/postscript media type in
for an example of such directives and how they should be described in a media type
registration.
All registrations MUST state whether or not they employ such "active content",
and if they do, they MUST state what steps have been taken to protect
users of the media type from harm.
Complex media types may include provisions for directives that institute
actions that, while not directly harmful to the recipient, may result in
disclosure of information that either facilitates a subsequent attack or else
violates a recipient's privacy in some way. Again, the registration of the
application/postscript media type illustrates how such directives can be
handled.
A media type that employs compression may provide an opportunity for
sending a small amount of data that, when received and evaluated, expands
enormously to consume all of the recipient's resources. All media types
SHOULD state whether or not they employ compression, and if they do they
should discuss what steps need to be taken to avoid such attacks.
A media type might be targeted for applications that require some sort of
security assurance but not provide the necessary security mechanisms
themselves. For example, a media type could be defined for storage of
confidential medical information that in turn requires an external
confidentiality service, or which is designed for use only within a
secure environment.
There are a number of additional requirements specific to the registration of
XML media types. These requirements are specified in .
Some transports impose restrictions on the type of data they can carry. For
example, Internet mail traditionally was limited to 7bit US-ASCII text.
Encoding schemes are often used to work around such transport limitations.
It is therefore useful to note what sort of data a media type can consist of
as part of its registration. An "encoding considerations" field is provided for
this purpose. Possible values of this field are:
The content of the media type consists solely of CRLF-delimited 7bit US-ASCII
text.
The content of the media type consists solely of CRLF-delimited 8bit text.
The content consists of unrestricted sequence of octets.
The content consists of a series of frames or packets without internal framing
or alignment indicators. Additional out-of-band information is needed to
interpret the data properly, including but not necessarily limited to,
knowledge of the boundaries between successive frames
and knowledge of the transport mechanism. Note that media types
of this sort cannot simply be stored in a file or transported as a simple
stream of octets; therefore, such media types are unsuitable for use
in many traditional protocols. A commonly used transport with framed encoding is the Real-time
Transport Protocol, RTP. Additional rules for framed encodings
defined for transport using RTP are given in .
Additional restrictions on 7bit and 8bit text are given in .
In the asynchronous mail environment, where information on the capabilities of
the remote mail agent is frequently not available to the sender, maximum
interoperability is attained by restricting the media types used to
those "common" formats expected to be widely implemented. This was asserted in
the past as a reason to limit the number of possible media types, and resulted
in a registration process with a significant hurdle and delay for those
registering media types.
However, the need for "common" media types does not require limiting the
registration of new media types. If a limited set of media types is recommended
for a particular application, that should be asserted by a separate
applicability statement specific for the application and/or environment.
Therefore, universal support and implementation of a media type is NOT a
requirement for registration. However, if a media type is explicitly intended
for limited use, this MUST be noted in its registration. The "Restrictions on Usage"
field is provided for this purpose.
Proposals for media types registered in the standards tree by the IETF itself
MUST be published as RFCs. RFC publication of vendor and personal media type
proposals is encouraged but not required. In all cases the IANA will retain copies
of all media type proposals and "publish" them as part of the media types
registration tree itself.
As stated previously, standards tree registrations for media types defined in
documents produced by other standards bodies MUST be described by a formal
standards specification produced by that body. Such specifications MUST
contain an appropriate media type registration template taken from
. Additionally, the
copyright on the registration template MUST allow the IANA to copy it into
the IANA registry.
Other than IETF registrations in the standards tree, the registration of a data
type does not imply endorsement, approval, or recommendation by the IANA or the
IETF or even certification that the specification is adequate. To become Internet
Standards, a protocol or data object must go through the IETF standards
process. This is too difficult and too lengthy a process for the convenient
registration of media types.
The standards tree exists for media types that do require a substantive
review and approval process in a recognized standards body.
The vendor and personal trees exist for those media types
that do not require such a process. It is expected that applicability statements
for particular applications will be published from time to time in the IETF,
recommending implementation of, and support for, media types that have proven
particularly useful in those contexts.
As discussed above, registration of a top-level type requires standards-track
processing in the IETF and, hence, RFC publication.
Various sorts of optional information SHOULD be included in the specification
of a media type if it is available:
Magic number(s) (length, octet values). Magic numbers are byte sequences that
are always present at a given place in the file and thus can be used to identify
entities as being of a given media type.
File name extension(s) commonly used on one or more platforms to indicate that some
file contains a given media type.
Mac OS File Type code(s) (4 octets) used to label files containing a given
media type.
Information about how fragment/anchor identifiers
are constructed for use in conjunction with this media type.
In the case of a registration in the standards tree, this additional information
MAY be provided in the formal specification of the media type. It is suggested
that this be done by incorporating the IANA media type registration form into the
specification itself.
The media type registration procedure is not a formal
standards process, but rather an administrative procedure
intended to allow community comment and sanity checking
without excessive time delay.
The normal IETF processes should be followed for all IETF
registrations in the standards tree. The posting of an
Internet Draft is a necessary first step, followed by
posting to the ietf-types@iana.org list as discussed below.
Registrations in the vendor and personal tree should be
submitted directly to the IANA, ideally after first
posting to the ietf-types@iana.org list for review.
Proposed registrations in the standards tree by other
standards bodies MUST be communicated to both the IESG (at
iesg@ietf.org) and to the ietf-types list (at ietf-types@iana.org).
Prior posting as an Internet Draft is not required for
these registrations, but may be helpful to the IESG and
is encouraged.
Notice of a potential media type registration in the standards tree MUST be sent to the
"ietf-types@iana.org" mailing list for review. This mailing list has been established
for the purpose of reviewing proposed media and access types. Registrations in
other trees MAY be sent to the list for review as well.
The intent of the public posting to this list is to solicit comments and
feedback on the choice of type/subtype name, the unambiguity of the references
with respect to versions and external profiling information, and a review of any
interoperability or security considerations. The submitter may submit a revised
registration or abandon the registration completely and at any time.
Media types registered in the standards tree MUST either be reviwed and
approved by the IESG or follow the Specification Required process:
Specification in a permanent and readily available public specification
Review and approval by the Designated Expert for media types
Provided that the media type meets all of the relevant requirements and has
obtained whatever approval this specification requires, the author may submit the
registration request to the IANA. Registration requests can be sent to
iana@iana.org. A web form for registration requests is also available:
Sending to ietf-types@iana.org does not constitute submitting
the registration to the IANA.
When the registration is either part of an RFC publication request or a
registration in the standards tree submitted to the IESG, close
coordination between the IANA and the IESG means IESG approval in
effect submits the registration to the IANA. There is no need for
an additional registration request in such cases.
Registrations submitted to the IANA will be passed on to the media types
reviewer. The media types reviewer, who is appointed by the IETF Applications
Area Director(s), will review the registration to make sure it meets the
requirements set forth in this document. Registrations that do not meet
these requirements will be returned to the submitter for revision.
Decisions made by the media types reviewer may be appealed to the IESG using
the procedure specified in section 6.5.4.
Once a media type registration has passed review, the IANA will register the
media type and make the media type registration available to the community.
Comments on registered media types may be submitted by members of the
community to the IANA at iana@iana.org. These comments will be reviewed by the media types
reviewer and then passed on to the "owner" of the media type if possible.
Submitters of comments may request that their comment be attached to the media
type registration itself, and if the IANA approves of this, the comment will be
made accessible in conjunction with the type registration.
Media type registrations are listed by the IANA at:
Upon receipt of a registration request, the IANA will submit the request for
Expert Review. The Expert Reviewer will check to see that the following
minimal conditions are met:
Media types MUST function as an actual media format. In particular, charsets
and transfer encodings MUST NOT be registered as media types.
All media types MUST have properly formed type and subtype names. All
type names MUST be defined by a standards-track RFC. All type/subtype name
pairs MUST be unique and MUST contain the proper tree prefix.
Types registered in the standards and personal trees MUST either provide a format
specification or a pointer to one.
All media types MUST have a reasonable security considerations section.
(It is neither possible nor necessary for the IANA to conduct a comprehensive
security review of media type registrations. Nevertheless, the IANA has the authority
to identify obviously incompetent material and return it to the submitter for revision.)
Registrations in the standards tree MUST satisfy the additional
requirement that they originate from the IETF itself or from another
Standards Body recognized as such by the IETF.
Registrations in the standards tree MUST satisfy the additional requirement that they
originate from the IETF itself or from another Standards Body recognized as such by
the IETF. The IESG determines whether or not a given organization qualifies as
a standards body.
Once a media type has been published by the IANA, the owner may request a change
to its definition. The descriptions of the different registration trees above
designate the "owners" of each type of registration.
The same procedure that would be appropriate for the original registration request is
used to process a change request.
Changes should be requested only when there are serious omissions or errors in
the published specification. When review is required, a change request may be
denied if it renders entities that were valid under the previous definition
invalid under the new definition.
The owner of a media type may pass responsibility
to another person or agency by informing the IANA and the ietf-types
list; this can be done without discussion or review.
The IESG may reassign responsibility for a media type. The most common case of
this will be to enable changes to be made to types where the author of the
registration has died, moved out of contact or is otherwise unable to make
changes that are important to the community.
Media type registrations may not be deleted; media types that are no
longer believed appropriate for use can be declared OBSOLETE by a
change to their "intended use" field; such media types will be clearly
marked in the lists published by the IANA.
Some discussion of Macintosh file type codes and their purpose can be found in
. Additionally, please refrain
from writing "none" or anything similar when no file extension or Macintosh
file type is specified, lest "none" be confused with an actual code value.
Someone wishing to define a +suffix name for a structured syntax for use with
a new media type registration SHOULD:
Check IANA's registry of media type name suffixes to see whether
or not there is already an entry for that well-defined structured syntax.
If there is no entry for their suffix scheme, fill out the template
(specified in )
and include that with the media type registration.
The template may be contained in an Internet Draft, alone or as part of
some other protocol specification. The template may also be submitted
in some other form (as part of another document or as a stand-alone
document), but the contents will be treated as an "IETF Contribution"
under the guidelines of RFC 3978.
Send a copy of the template or a pointer to
the containing document (with specific reference to the section with
the template) to the mailing list
ietf-types@ietf.org,
requesting review.
This may be combined with a request to review the media type registration.
Allow a reasonable time for discussion and comments.
Respond to review comments and make revisions to the proposed registration
as needed to bring it into line with the guidelines given in this document.
Submit the (possibly updated) registration template (or pointer to document
containing it) to IANA at iana@iana.org.
Upon receipt of a structured syntax suffix registration request,
IANA checks the submission for completeness; if
sections are missing or citations are not correct, IANA rejects the
registration request.
IANA checks the current registry for a entry
with the same name; if such a registry exists, IANA rejects the
registration request.
IANA requests Expert Review of the
registration request against the corresponding guidelines.
The Designated Expert may request additional review
or discussion, as necessary.
If Expert Review recommends registration registration, IANA adds the registration to the
appropriate registry.
Registrations may be updated in each registry by the same mechanism
as required for an initial registration. In cases where the original
definition of the scheme is contained in an IESG-approved document,
update of the specification also requires IESG approval.
This template describes the fields that must be supplied in a structured syntax
sufficx registration request:
Full name of the well-defined structured syntax.
Suffix used to indicate conformance to the syntax.
Include full citations for all specifications necessary to understand
the structured syntax.
General guidance regarding encoding considerations for any type employing
this syntax should be given here. The same requirements for media type
encoding considerations given in apply here.
Any issues regarding the interoperable use of types employing this
structured syntax should be given here.
Examples would include the existence of incompatible versions of the syntax,
issues combining certain charsets with the syntax, or incompatibilities with
other types or protocols.
Security considerations shared by media types employing this structured
syntax must be specified here. The same requirements for media type
security considerations given in apply here,
with the exception that option of not assessing the security considerations
is not available for suffix registrations.
Person (including contact information) to contact for further information.
Person (including contact information)
authorized to change this suffix registration.
Security requirements for media type registrations are discussed in
.
The purpose of this document is to define IANA registries for media types and
structured syntax suffixes.
The current authors would like to acknowledge their debt
to the late Dr. Jon Postel, whose general model of IANA
registration procedures and specific contributions
shaped the predecessors of this document . We hope that
the current version is one with which he would have
agreed but, as it is impossible to verify that
agreement, we have regretfully removed his name as a
co-author.
Alexey Melnikov provided many helpful review comments and suggestions.
Mac OS: File Type and Creator Codes, and File FormatsApple Computer, Inc.
A number of media types with unfaceted names, registered prior to 1996, would,
if registered under the guidelines in this document, be given a faceted name
and placed into either the vendor or personal
trees. Reregistration of those types to reflect the appropriate trees is
encouraged but not required. Ownership and change control principles
outlined in this document apply to those types as if they had been registered
in the trees described above.
From time to time there may also be cases where a media type with an unfaceted
name has been widely deployed without being registered. If possible such types
SHOULD be reregistered with a proper faceted name. However, if this is not
possible the type can, subject to approval by both the media types reviewer and
the IESG, be registered in the proper tree with its unfaceted name.
Suffixes to indicate the use of a particular structured syntax are now fully
specified and a suffix registration process has been defined.
Registration of widely deployed unregistered unfaceted type names in the vendor
or personal trees is now allowed, subject to approval by the media types
reviewer and the IESG.
The standards tree registration process has been revised to include Expert
Review and generalized to address cases like media types in non-IETF stream
documents.
A field for fragment/anchor identifiers has been added to the registration template.