Registration of media type application/ttaf+xml

Silvia Pfeiffer silviapfeiffer1 at
Tue Oct 6 03:03:20 CEST 2009

I am concerned about the lack of a additional information typically
used in mime type registration RFCS, see e.g. (for 3gpp) or (mpeg4) or (ogg):

Magic number(s):  (probably not relevant)
File extension(s):
Macintosh File Type Code(s):

I think it is important that we specify a common file extension and a
mac file type code so as not to create confusion in the market with
some people creating .dfxp , some creating .xml and some creating
whatever they think is appropriate. This will make it very difficult
for example for Web servers to serve the correct mime types, since
they tend to do so based on file extensions.

My suggestion is:

File extension: .dfxp (I think four letters is reasonable nowadays,
even for windows?)

Mac file type code: DFXP

Best Regards,

On Thu, Oct 1, 2009 at 6:46 AM, Philippe Le Hegaret <plh at> wrote:
> The following media type registration will be submitted to
> the IESG for review, approval, and registration with IANA (as per [1]).
> At this point, we would appreciate comments on this registration
> information.  If you see any problems, please let us know.
> Regards,
> Philippe
> [1]
> [[
> This appendix registers a new MIME media type, "application/ttaf+xml"
> in conformance with [1144]BCP 13 and [1145]W3CRegMedia. The information
> in this appendix is being submitted to the Internet Engineering
> Steering Group (IESG) for review, approval, and registration with the
> Internet Assigned Numbers Authority (IANA).
>    [1144]
>    [1145]
>   MIME media type name:
>          application
>   MIME subtype name:
>          ttaf+xml
>   Required parameters:
>          None.
>   Optional parameters:
>          The encoding of a TT AF document must be determined by the
>          XML encoding declaration. This has identical semantics to the
>          application/xml media type in the case where the charset
>          parameter is omitted, as specified in [1146][XML Media],
>          Sections 8.9, 8.10 and 8.11.
>          The document profile of a TT AF document may be specified
>          using an optional profile parameter, which, if specified, the
>          value of which must adhere to the syntax and semantics of
>          ttp:profile parameter defined by Section [1147]6.2.8
>          ttp:profile of the published specification.
>   Encoding considerations:
>          Same for application/xml. See [1148][XML Media], Section 3.2.
>   Restrictions on usage:
>          None.
>   Security considerations:
>          As with other XML types and as noted in [1149][XML Media]
>          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 TT AF
>          and of XML in general, it is possible that
>          "application/ttaf+xml" may describe content that has security
>          implications beyond those described here. However, if the
>          processor follows only the normative semantics of the
>          published specification, this content will be outside TT AF
>          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.
>   Interoperability considerations:
>          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 TT AF namespaces and in other namespaces.
>          Because TT AF is extensible, conformant
>          "application/ttaf+xml" processors must expect 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.
>   Published specification:
>          This media type registration is extracted from Appendix
>          [1150]D Media Type Registration of the [1151]Timed Text (TT)
>          Authoring Format 1.0 - Distribution Format Exchange Profile
>          (DFXP) specification.
>    [1151]
>   Additional information:
>          None.
>   Person & email address to contact for further information:
>          Glenn Adams (public-tt at
>   Intended usage:
>          COMMON
>   Author/Change controller:
>          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.
> ]]

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