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This is an archived WebSchemas proposal Accessibility schema for schema.org. See Proposals listing for more. Note: active schema.org development is now based at github


Making Accessible Content Discoverable

The A11yMetadata Project seeks to extend schema.org by including new properties to address the accessibility and discoverability of resources on the Web.

A majority of properties and terms in this proposal are a subset derived from the IMS Global Learning Consortium's Access For All specification. IMS Global Learning Consortium has licensed these properties to schema.org under the Creative Commons Attribute-ShareAlike License (version 3.0) so that they can be used under schema.org‘s corresponding terms and conditions. Any other organizations or initiatives that would like to adopt IMS Global’s AccessForAll for other purposes are requested to coordinate directly with IMS Global.

V.5 was submitted on April 15, 2013

V.6 was finalized on September 8, 2013. The major changes are simplifications: moving displayTransformability from a property to a property value of mediaFeature, adding a few more mediaFeature properties, reordering some items and making clear that two properties are only for use on softwareApplication and its subclasses. This simplicity does not detract from the information model, but eases adoption. The two samples were also updated to reflect these changes.

There is now an Open Issues wiki page that will track issues as we drive to completion. Open items will be noted on this page, and the tracker will contain them all.


(Definitions for most of the expected values can be found in the IMS Global Access for All (AfA) Information Model Data Element Specification.)

Property Expected Type Expected Values Description
accessMode Text
  • auditory
  • colorDependent
  • tactile
  • textOnImage
  • textual
  • visual
An access mode through which the intellectual content of a described resource or adaptation is communicated; if adaptations for the resource are known, the access modes of those adaptations are not included.
mediaFeature Text
  • alternativeText
  • audioDescription
  • braille
  • captions
  • ChemML
  • describedMath
  • displayTransformability
  • haptic
  • highContrast
  • largePrint
  • latex
  • longDescription
  • MathML
  • musicBraille
  • nemethBraille
  • signLanguage
  • structuralNavigation
  • tactileGraphic
  • tactileObject
  • transcript
Content features of the resource, such as accessible media and alternatives.
hasAdaptation URL Identifier of a resource that is an adaptation, for accessibility purposes, for this resource.
isAdaptationOf URL Identifier of a resource for which this is an adaptation for accessibility purposes.
accessHazard Text
  • flashing
  • motionSimulation
  • sound
A characteristic of the described resource that is physiologically dangerous to some users. This is related to WCAG 2.0 guideline 2.3

Accessibility Additions to only SoftwareApplication

Property Expected Type Expected Values Description
ATCompatible Boolean The resource is compatible with assistive technologies. For example, that the resource complies to WCAG 2.0 checkpoints: 1.1.1, 1.3.1, 1.3.2, 2.4.4, 3.1.1, 3.1.2, 3.3.2, 4.1.1, 4.1.2.
accessAPI Text
  • AndroidAccessibility
  • ARIA
  • ATK
  • AT-SPI
  • BlackberryAccessibility
  • iAccessible2
  • iOSAccessibility
  • JavaAccessibility
  • MacOSXAccessibility
  • MSAA
  • UIAutomation
Indicates that the resource is compatible with the referenced accessibility API.
controlFlexibility Text
  • fullAudioControl
  • fullKeyboardControl
  • fullMouseControl
  • fullTouchControl
  • fullVideoControl
Identifies one or more input methods can be used that allow access to all of the application functionality.

Extensions of bookFormatType

This proposal also requests the expansion of the bookFormatType enumeration to include the following specializations of EBook:

  • DAISY202
  • DAISY3
  • EPUB2
  • EPUB3

Access Mode and Media Feature Framework: a tabular view

Note that this section can be used in two ways. The first is to understand the mediaFeatures, and to have a sensory framework to understand them within. The second is to explain accessMode. Use this section as you wish.

A perusal of the properties above, especially mediaFeature and accessMode gives you a set of pieces without a plan. There is an overall plan, which is be explained in the table below. Before the details, though, I should explain

  1. AfA for electric learning resources
  2. This effort extended this for ebooks (richer content) and to physical books and media as well.

The framework held up well, but there are many attributes that get in the way of a simple model.

The first concept is access modes. These are the way in which the intellectual content of a described resource or adaptation is communicated. There are four defined in the specification: visual, auditory, tactile and textual. The input access modes are specified in the left column. There is also the concept of a refinement on an access mode. ColorDependent, for example, says that colors, which may be hard to recognize if colorblind, are present and significant in the visual appearance and intellectual information of the content.

The access mode at the top of the table (row 2, columns 4-7 are the access modes that adapted content is available in. The intersection of the two is the adaptation available to make that transformation. For example, an audio recording can be made available in textual form through captions or a transcript. It's "input at the left, transformation in the middle of the table, output access mode at the top."

It's worthwhile to try a few examples.

  1. A video with audio can be made available as purely visual/textual by sign language or captions.
  2. A book with mathematics (commonly presented as visual images) can be made accessible if the text is made available as text and the mathematics available through the long list of alternatives from describedMath and longDescription to MathML and laTex.

Note that math is in row 6 under visual (as this is how it was typically done in the past… inaccessible images). The qualified access mode in italics and the italic qualifier names are not access modes in the content (we just think of them as images), but calling them out as special content types puts the adaptation types (mediaFeatures) in a better organization. Likewise, putting the various braille mediaFeatures under tactile puts the values in a better context. Note that some ebook software also has the capability to present text in braille format with appropriate devices.

There is one other concept to bring up: mediaFeatures that are associated with a specific access mode. This is row 3 of the table. The first one, and easiest to understand, is largePrint. Printed books or images will have a large print adaptation available, no matter what the input access mode was. Textual has a few, with displayTransformability and structuralNavigation calling out specific points of WCAG (site the sections). These optional attributes will be true for any textual representation.

Finally, note that the mediaFeatures can be divided into three categories.

  1. Display or Transformative - restyling, adjusting layout, while staying within the same access mode. This is row 3 of the table.
  2. Augmentation or Content - adding captions, descriptions, alt-text to augment an accessMode to another accessMode. This is the bulk of the table, from row 4 column 4, down and to the right.
  3. Symbolic encodings - as noted above, MathML, ChemML and laTex are specific encodings of symbologies. having them in their own content rows (along with nemethBraille).

The hope is that, once you have seen the mediaFeatures in this organized fashion, that they'll make more sense. This framework also leaves clear places where other mediaFeatures could be placed in the future.

Content Access modes and adaptations Searchable Access mode
Access Modes Visual (V) Auditory (A) Tactile (B) Textual (T)
Refined Access Mode Refinement name +largePrint, +highContrast +haptic +displayTransformability, +structuralNavigation
Visual, including photos, graphs and charts ALWAYS audioDescription tactileGraphic, tactileObject, altText, longDescription alternativeText, longDescription
(textual) textOnImage braille alternativeText, longDescription
(mathematical) mathOnImage audioDescription tactileGraphic, tactileObject, nemethBraille alternativeText, longDescription, describedMath, MathML, laTex
(chemical) chemOnImage audioDescription tactileGraphic, tactileObject, nemethBraille alternativeText, longDescription, ChemML
(musical) musicOnImage musicBraille
colorDependent captions audioDescription alternativeText, longDescription
Auditory signLanguage, captions (open) ALWAYS captions, transcript
Tactile ALWAYS
Textual ALWAYS

A few notes of future things that could be done.

  1. Looking at this framweork, it's unclear that we need highContrast as a mediaFeature. It's really just a type of displayTransformability and belongs over in textual as such. Thoughts?
  2. Small consistency thought. Consider that all of the "on image" and colorDependent names would be more clear if the refinement name said "onVisual" at the end instead of "onImage" (good idea for some point in the future... not worth acting on)

Example Markup

Example 1 (Book)

The following example shows how the accessibility metadata will be used to enhance Bookshare records. Note that our markuup has advanced since this early illustrative example. A description and the process and a corpus of searchable books can be found at the accessibility metadata website.

More examples are referenced in the Discussion and Related Work section.

  1. <div itemscope="" itemtype="http://schema.org/Book">
  2.    <link rel="bookFormat" href="http://schema.org/EBook/DAISY3"/>
  3.    <meta itemprop="accessMode" content="textual"/>
  4.    <meta itemprop="accessMode" content="visual"/>
  5.    <meta itemprop="isAdaptationOf" content="urn:isbn:9780030426599"/>
  6.    <meta itemprop="ATCompatible" content="true">
  7.    <meta itemprop="mediaFeature" content="displayTransformability">
  8.    <meta itemprop="mediaFeature" content="longDescription">
  9.    <meta itemprop="mediaFeature" content="alternativeText">
  11.    <dl>
  12.       <dt>Brief Synopsis:</dt>
  13.       <dd itemprop="description">NIMAC-sourced textbook</dd>
  14.       <dt>Long Synopsis:</dt>
  15.       <dd>N/A</dd>
  16.       <dt>Book Quality:</dt>
  17.       <dd>Publisher Quality</dd>
  18.       <dt>Book Size:</dt>
  19.       <dd itemprop="numberOfPages">598 Pages</dd>
  20.       <dt>ISBN-13:</dt>
  21.       <dd itemprop="isbn">9780030426599</dd>
  22.       <dt>Publisher:</dt>
  23.       <dd itemprop="publisher" itemtype="http://schema.org/Organization" itemscope="">Holt, Rinehart and Winston</dd>
  24.       <dt>Date of Addition:</dt>
  25.       <dd>06/08/10</dd>
  26.       <dt>Copyright Date:</dt>
  27.       <dd itemprop="copyrightYear">2007</dd>
  28.       <dt>Copyrighted By:</dt>
  29.       <dd itemprop="copyrightHolder" itemtype="http://schema.org/Organization" itemscope="">Holt, Rinehart and Winston</dd>
  30.       <dt>Adult content:</dt>
  31.       <dd><meta itemprop="isFamilyFriendly" content="true"/>No</dd>
  32.       <dt>Language:</dt>
  33.       <dd><meta itemprop="inLanguage" content="en-US"/>English US</dd>
  34.       <dt>Essential Images:</dt>
  35.       <dd>861</dd>
  36.       <dt>Described Images:</dt>
  37.       <dd>910</dd>
  38.       <dt>Categories:</dt>
  39.       <dd><span itemprop="genre">Educational Materials</span></dd>
  40.       <dt>Grade Levels:</dt>
  41.       <dd>Sixth grade, Seventh grade, Eighth grade</dd>
  42.       <dt>Submitted By:</dt>
  43.       <dd>Bookshare Staff</dd>
  44.       <dt>NIMAC:</dt>
  45.       <dd>This book is currently only available to public K-12 schools and organizations in the United States for use with students with an IEP, because it was created from files supplied by the NIMAC under these restrictions. Learn more in the NIMAC Support Center.</dd>
  46.    </dl>
  48.    <div class="bookReviews" itemprop="aggregateRating" itemscope itemtype="http://schema.org/AggregateRating">
  49.       <h2>Reviews of Holt Physical Science (<span itemprop="reviewCount">0</span> reviews)</h2>
  51.       <div class="bookReviewScore">
  52.          <span><span itemprop="ratingValue>0</span> - No Rating Yet</span>
  53.       </div>
  54.    </div>
  55. </div>

(The source record can be found at https://www.bookshare.org/browse/book/190639.)

Example 2 (Video)

This example shows how the accessibility metadata can be used to augment a record for a video:

  1. <dl itemtype="http://schema.org/VideoObject" itemscope="">
  2.   <dt>Title:</dt>
  3.   <dd itemprop="name">Arctic Climate Perspectives</dd>
  4.   <dt>Description:</dt>
  5.   <dd itemprop="description">This video, adapted from material provided by the ECHO partners,
  6.     describes how global climate change is affecting Barrow, Alaska.</dd>
  7.   <dt>Adaptation Type:</dt>
  8.   <dd><span itemprop="mediaFeature">captions</span></dd>
  9.   <dt>Access Mode:</dt>
  10.   <dd><span itemprop="accessMode">auditory</span>, <span itemprop="accessMode">visual</span></dd>
  11.   <dt>URL:</dt>
  12.   <dd><a itemprop="url" href="http://www.teachersdomain.org/asset/echo07_vid_climate">http://www.teachersdomain.org/asset/echo07_vid_climate</a>/</dd>
  13.   <dt>Has Adaptation:</dt>
  14.   <dd><a itemprop="hasAdaptation" href="http://www.teachersdomain.org/asset/echo07_vid_climate_dvs/">http://www.teachersdomain.org/asset/echo07_vid_climate_dvs/</a></dd>
  15.   <dt>Subjects:</dt>
  16.   <dd><span itemprop="about">National K-12 Subject::Science::Earth and Space Science::Water Cycle, Weather,
  17.     and Climate::Structure and Composition of the Atmosphere, National K-12 Subject::Science::Earth and
  18.     Space Science::Water Cycle, Weather, and Climate::Climate</span></dd>
  19.   <dt>Education Level:</dt>
  20.   <dd>Grade 6, Grade 7, Grade 8, Grade 9</dd>
  21.   <dt>Audience:</dt>
  22.   <dd><span itemprop="intendedEndUserRole">Learner</span></dd>
  23.   <dt>Resource Type:</dt>
  24.   <dd><span itemprop="genre">Audio/Visual</span>, <span itemprop="genre">Movie/Animation</span></dd>
  25.   <dt>Language:</dt>
  26.   <dd><span itemprop="inLanguage">en-US</span></dd>
  27.   <dt>Publication Date:</dt>
  28.   <dd itemprop="datePublished">2007-02-12</dd>
  29.   <dt>Rights:</dt>
  30.   <dd>Download and Share, <a itemprop="useRightsUrl" href="http://www.teachersdomain.org/oerlicense/2/">http://www.teachersdomain.org/oerlicense/2/</a></dd>
  31. </dl>

Issues Tracker and Open Issues

Issue Tracker, both open and closed

This list will be updated afte rthe first meeting

  • stuff (referring to open items, by name and number)

Discussion and Related Work