This document defines
type and provides a registry of compact (short) identifiers that may be
used to identify TTML processor profiles. A processor profile specifies
a set of capabilities that a processor must support in order to process
a document, where this profile may be defined in a specification
Profile Definition Document, inline within a TTML Document Instance,
or by using a combination of these methods. This document only
considers the first two of these methods since the third method (the use
of inline profile definitions) is not considered to be an identifiable,
shared profile definition, but rather, a private profile definition
scoped to the document instance in which it is defined.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.
This document was published by the Timed Text Working Group as a Working Group Note.
Comments regarding this document are welcome.
Please send them to
[TTML-Profile-Registry] at the start of your
Publication as a Working Group Note does not imply endorsement by the W3C Membership.
This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 1 August 2017 W3C Patent Policy.
This document is governed by the 15 September 2020 W3C Process Document.
This section is non-normative.
This document serves two purposes: (1) to define the Media Type
application/ttml+xml, and (2) to define a registry
of compact (short) identifiers of TTML processor profiles.
As a registry, this document is intended to provide a central location for enumerating identified TTML processor profiles, or, more strictly speaking, TTML decoder/processors, where each entry in the registry identifies a particular profile which is understood to implement a processor capable of satisfying the constraints of a defined TTML processor profile that takes the form of a TTML Profile Definition Document. By utilizing a common registry, it is possible to avoid name collisions among different profile defining fora.
In the context of this registry, the term profile
means processor profile. It explicitly does not
mean content profile. That is, nothing about the use
codecs parameters described here is
intended to be used to identify or make claims about whether
a TTML resource conforms with a TTML Content Profile or any
type of TTML Profile that may be interpreted in whole or in
part as making statements about the conformance of a TTML
resource or the features of TTML (or other external
specifications) actually used in the resource.
Applications using the entries in this registry are encouraged to support
codecs parameter value syntax is defined as
codecs-parameter-value as follows,
expressed using the syntax expression conventions defined by §2.3 of [TTML2-1e].
identifier : element // element defined by [RFC6381] // where "+", "|" and "." are prohibited characters // ("." is reserved as a hierarchy delimiter in [RFC6381]) and-group : identifier ["+" identifier]* // no linear white-space is implied or permitted // between each token codecs-parameter-value : and-group ["|" and-group]* // no linear white-space is implied or permitted // between each token
codecs parameter may
employ either (or both) of two combination operators,
+ (AND) and
| (OR), which may be
used to specify, respectively, that all processor profiles apply
(simultaneously) or that any processor profile of a list of profiles may
apply individually. If both operators are used, then
+ operator has precedence.
are intended to have semantics equivalent to
all(...) and the
function syntax supported by
ttp:processorProfiles attribute as defined by
[TTML2-1e], §6.2.8. Take note, however, that the
combined use of both
ttp:processorProfiles attribute value
expression is not directly supported by [TTML2-1e], and,
therefore, an application that encounters a combination of
both operators in a
codecs value expression will
need to process such combination semantics as a higher level
protocol outside the scope of [TTML2-1e] semantics.
A+B|C+D|E specifies that a TTML processor that implements
any one of the
E processor profiles satisfies
the requirements to fetch and begin decode/processing of a TTML
X+Y means that both
Y processor profiles must be
X|Y means that either
Y processor profile must be
codecs string for specifying either a TTML processor that supports
[IMSC1.0.1] Text Profile or one that supports [EBU-TT-D-1]
codecs string for specifying a TTML processor that supports
the union of sets of required features of both
[IMSC1.0.1] Text Profile and [EBU-TT-D-1]
This section defines the media type "application/ttml+xml", and, in conformance with BCP 13 and W3CRegMedia, serves as the registration thereof with the Internet Assigned Numbers Authority (IANA).
This updated definition supersedes the initial registration information specified in [TTML1-1e], Appendix C, as updated by [TTML1-2e], Appendix C.
If specified, the
charset parameter must match the XML
encoding declaration, or if absent, the actual encoding. See also Encoding
The document profile of a TTMLDocument Instance may be specified using
profile parameter, which, if specified, the value
of which must adhere to the syntax and semantics of
ttp:profile parameter defined by TTML 1.0 Second Edition, Section 6.2.8 ttp:profile of the published specification.
codecs parameter provides a
short form version of the
parameter with multiple-profile combinatorial
capability. If a short (4-character) form of a profile
is registered in
Profile Registry, it is recommended that
codecs parameter be used and not
profile parameter. The nominal value
of this parameter is a single 4 character code from
Additionally, applications using the entries in the registry are encouraged to adopt the following combination syntax:
Employ two combination operators, '+' (AND) and '|' (OR), which may be used to specify, respectively, that multiple processor profiles apply (simultaneously) or that any processor profile of a list of profiles may apply individually. If both operators are used in a codecs value, then the '+' operator has precedence.
The example: "A+B|C+D|E" states that a TTML processor that implements any one of A+B or C+D or E processor profiles satisfies, at first order, the requirements to fetch and begin decode/processing of a TTML document, where X+Y means that both X and Y processor profiles must be supported, and X|Y means that either X or Y processor profile must be supported.
Same for application/xml, except constrained to either UTF-8 or UTF-16. See IETF RFC 7303, XML Media Types, Section 3.2. For the purpose of filling out the IANA Application for Media Type (http://www.iana.org/cgi-bin/mediatypes.pl), the value binary applies.
As with other XML types and as noted in IETF RFC 7303, XML Media Types, Section 10, repeated expansion of maliciously constructed XML entities can be used to consume large amounts of memory, which may cause XML processors in constrained environments to fail.
In addition, because of the extensibility features for TTML and of XML in general, it is possible that "application/ttml+xml" may describe content that has security implications beyond those described here. However, TTML does not provide for any sort of active or executable content, and if the processor follows only the normative semantics of the published specification, this content will be outside TTML namespaces and may be ignored. Only in the case where the processor recognizes and processes the additional content, or where further processing of that content is dispatched to other processors, would security issues potentially arise. And in that case, they would fall outside the domain of this registration document.
Although not prohibited, there are no expectations that XML signatures or encryption would normally be employed.
The published specification describes processing semantics that dictate behavior that must be followed when dealing with, among other things, unrecognized elements and attributes, both in TTML namespaces and in other namespaces.
Because TTML is extensible, conformant "application/ttml+xml" processors may expect (and enforce) that content received is well-formed XML, but it cannot be guaranteed that the content is valid to a particular DTD or Schema or that the processor will recognize all of the elements and attributes in the document.
This media type registration is extracted from the TTML Profile Registry.
TTML is used in the television industry for the purpose of authoring, transcoding and exchanging timed text information and for delivering captions, subtitles, and other metadata for television material repurposed for the Web or, more generally, the Internet.
There is partial and full support of TTML in components used by several Web browsers plugins, and in a number of caption authoring tools.
For documents labeled as application/ttml+xml, the fragment identifier notation is intended to be used with xml:id attributes, as described in section 7.2.1 of the Timed Text Markup Language 1 (TTML1) specification.
Timed Text Working Group (firstname.lastname@example.org)
The published specification is a work product of the World Wide Web Consortium's Timed Text (TT) Working Group.
The W3C has change control over this specification.
Each entry must include a unique identification, where the
scope of uniqueness is the set of identifiers defined in
this registry. An identifier must conform with
element non-terminal of [RFC6381]
and, furthermore, may not contain any of the characters in the regular
expression character class
An update to this registry is an addition, change or deletion of an entry. Any person can request an update to this registry by email notice to the chairman of the Timed Text Working Group who will place it on an upcoming meeting agenda and notify the requestor. Consideration and disposition of the request is by consensus of the W3C Timed Text Working Group. The Chair will then notify the requestor of the outcome and update the registry accordingly. Although profiles can be deleted, there is no intent to re-use deleted profile values. That is, the intent is that profile entries are "stable".
This section is the registry of short form profile identifiers. The first sub-section details how such identifiers should be dereferenced to profile designators, the specifications that define those profiles, and the contact organisation for each profile. The second sub-section describes the mechanism used by each profile to permit identification of the profile of a TTML Document Instance by inspection of that document.
The following table defines the Profile Designator for each short form Profile Identifier in this Registry, alongside the public specification document in which the profile is defined, and the relevant contact organisation. Entries are ordered alphabetically according to the short profile identifier.
|Profile Identifier||Profile Designator||Public Specification(s)||Requestor Contact|
||IRT Technical Guidelines||IRT|