Decision on CfC: XR Device API Review


Only messages supporting the draft APA comment below have been received.
This Call for Consensus is consequently agreed to as an APA decision
according to our published process and our comment will now be forwarded
to the Immersive Web WG.

The head of thread for this CfC is at:



Janina Sajka writes:
> Colleagues:
> This is a Call for Consensus (CfC) to the Accessible Platform
> Architectures (APA) Working Group concerning  our draft response to the
> Immersive Web Working Group on their requested accessibility review[1]
> of their XR Device API specification:
> ***Draft Comment***
> Thank you for requesting our review of your XR Device API from an
> accessibility perspective. Our response today is based on a close
> reading of this specification by two APA members[2] and a subsequent
> discussion of their findings during a regularly scheduled APA
> teleconference.[3]
> We have found no explicit accessibility problems in this specification,
> so we have no objection to it moving forward toward W3C recommendation
> status as currently specified.
> However, our review has raised a series of questions and concerns, and
> we will now look for opportunities to engage with you to establish a
> fuller understanding of accessibility opportunities and challenges in XR
> technology, as well as greater support for accessibility use cases in
> future revisions of your specifications. A significant concern for us is
> the question of how semantically rich representations of XR are to be
> provided? Semantic constructs are critical to supporting accessibility.
> APA wishes to acknowledge our great interest in the emerging XR
> technology.  Toward that end an initial  request for a joint meeting
> during TPAC is forthcoming. We are also happy to see the announcement of
> a W3C Workshop on "Inclusive Design for Immersive Web."[4]
> We look forward to working with you more directly as XR matures.
> ***       ACTION TO TAKE***
> This CfC is now open for objection, comment, as well as statements of
> support via email. Silence will be interpreted as support, though
> messages of support are certainly welcome.
> If you object to this proposed action, or have comments concerning this
> proposal, please respond by replying on list to this message no
> later than 23:59 (Midnight) Boston Time, Friday 6 September.
> Best,
> Janina
> NOTE: This Call for Consensus is being conducted in accordance with the
> APA Decision Policy published at:
> [1]
> [2]
> [3]
> [4]
> ------------------------------------------------------------------------------
> Janina Sajka
> Linux Foundation Fellow
> Executive Chair, Accessibility Workgroup:
> The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI)
> Chair, Accessible Platform Architectures

>    Here is my proposed feedback to the Timed Text Working Group:
>    <draft-feedback>
>     1. While we appreciate that [1]TTML Profiles for Internet Media
>        Subtitles and Captions 1.1 is depending on [2]Timed Text Markup
>        Language 2 (TTML2), it should still include an introduction that
>        guides the reader to a better understanding of its content.  Such
>        an introduction could respond to the following questions:
>     a. Why are profiles needed for text-only and image-only
>        captions/subtitles?
>     b. What are typical use cases for a image-only captions/subtitles?
>     c. What is the purpose of a presentation processor, and a
>        transformation processor?
>     2. There is a general issue with the way that an author specifies
>        layout characteristics of captions and subtitles, such as font
>        size, font family, line height, background and positioning.  The
>        spec describes the approach of the author specifying a “fixed
>        layout” for captions and subtitles that the user cannot change.
>        However, it must be possible for the user to overwrite the author’s
>        choice of font size, or background color, for example. This is
>        necessary for accessibility reasons, in the same way that browsers
>        allow the user to change font size and background color.  How can
>        we find a good solution for these conflicting interests between
>        author and user?  We would like to get into a discussion with you
>        on this issue.
>     3. Section 2 Documentation Conventions (applies also to [3]Timed Text
>        Markup Language 2 (TTML2) section 2.3). For accessibility of the
>        spec, information such as whether an element is deprecated or
>        obsoleted should not be indicated by color (or background color)
>        alone (cf. [4]WCAG 2.0 SC 1.4.1).
>     4. Section 5.1 General. The method of associating a text profile
>        document instance with an image profile document instance should be
>        specified for interoperability reasons, and not be left open to the
>        specific implementation.  Also, the association should be in both
>        ways, i.e. also from the image profile document instance to the
>        text profile document instance.
>     5. Section 6 Supported Features and Extensions. All font-related
>        features are prohibited for the image profile. This seems to be an
>        unnecessary restriction if the image profile contains images in SVG
>        format which could be rendered differently based on the author’s
>        choice of font characteristics.
>     6. Section 7.7.3 itts:forcedDisplay. This seems like a temporary
>        solution. Wouldn’t it be better to define semantic layers of
>        information that each could be made visible and invisible at
>        runtime as appropriate for the user?  For example, the user may
>        want to see either speech-only (subtitles), narration speech only
>        (parts of subtitles), foreign-language speech-only (parts of
>        subtitles) or any combination of them.
>     7. Section 7.7.4 itts:altText.  While we see this feature as useful
>        for accessibility purposes, it should be mandatory for images
>        rather than recommended only. As mentioned in the spec, one could
>        take the pertaining text passage from the text profile document
>        instance – but (1) an accompanying text profile is not required,
>        and (2) the alternative text for the image could be different from
>        the textual caption. Therefore, the itts:altText element should
>        always be specified, but it should be empty for decorative images
>        (not clear if a “decorative image” used as a caption makes sense
>        anyway). By requiring an itts:altText for every image, but allowing
>        for an empty element in case of a decorative image, we would align
>        it with the alt attribute in HTML5 for images.
>    </draft-feedback>
>    Best regards,
>    Gottfried
>    -----Ursprüngliche Nachricht-----
>    Von: Accessible Platform Architectures Working Group Issue Tracker
>    []
>    Gesendet: Mittwoch, 18. Oktober 2017 09:29
>    An:
>    Betreff: apa-ACTION-2152: Review ttml profiles for internet media
>    subtitles and captions 1.1
>    apa-ACTION-2152: Review ttml profiles for internet media subtitles and
>    captions 1.1 [5]
>    [6]
>    Assigned to: Gottfried Zimmermann
> References
>    1.
>    2.
>    3.
>    4.
>    5.
>    6.


Janina Sajka

Linux Foundation Fellow
Executive Chair, Accessibility Workgroup:

The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI)
Chair, Accessible Platform Architectures

Received on Tuesday, 3 September 2019 18:49:21 UTC