Draft proposal for alt text for non-text elements for review by theaccessibility subteam

[Richard Schwerdtfeger <schwer@us.ibm.com>]

Executive Summary of proposed changes addressing alternative text for non-text elements:

An accessibility gap in the ODF specification is alternative text support for non-text objects. This is also a key accessbility requirement in the W3C Web Content Accessibility Guidelines. In order to address this, the subteam has decided we need provisioning for alternative text and long descriptions for these types of ODF elements. To minimize the impact to the ODF 1.0 specification we will attempt to use the draw:name property for alternative text and <svg:desc> element, from SVG for the long description. We have also decided that ODF captions do not follow standard XML in that the captioning <text:sequence> does not show a normative relationship, in the specification, to the drawing object being captioned. As a result we will be introducing a new draw:describedBy attribute to apply to objects being captioned.

Furthermore, we will be asking that the appropriate text be added to the ODF specification to indicate how this accessibility meta data is mapped by the authoring tool to platform accessibility API as well as their accessibility applicability in the specification.

Requirements:

1.0 image-map elements
The draw:name attribute must be provided as an optional attribute to the following:

draw:area-rectangle
draw:area-circle
draw:area-polygon

Text should be added to these elements as follows:

for the name attribute,

draw:name is used as a short accessible name for alternative text. When transcoding from another document format to ODF the alt text shall be mapped to the draw:name attribute.

<svg:desc> Is used for the long description in support of accessibility.

2.0 Drawing layer

The <svg:desc> attribute must be provided as an optional attribute to the <draw:layer>. This attribute must apply to all ODF document formats for which <draw:layer> is used.

for the name attribute,

draw:name is used as a short accessible name for alternative text. When transcoding from another document format to ODF the alt text shall be mapped to the draw:name attribute.

<svg:desc> Is used for the long description in support of accessibility.

Note: when transcoding from another document format to ODF the alt text shall be mapped to the draw:name attribute.

3.0 General wording to be added

Where <draw:param> is specified it should be indicated that neither draw:name or <svg:desc> are to be used for accessibility.

4.0 Drawing shapes (line 5926 of spec.)

The draw:name attribute, and <svg:desc> attribute must be provided as an optional attribute to all drawing shape elements defined below. Note: draw:name is provided and stored by both IBM Workplace and Open Office 2.0 for presentations (Impress). However, the name attribute does not appear in the Writer application. These attributes must apply to all ODF document formats for which these elements are used.

The following are the drawing shape elements:

<draw-rect>
<draw:line>
<draw:polyline>
<draw:polygon>
<draw:regular-polygon>
<draw:path>
<draw:circle>
<draw:ellipse>
<draw:g>
<draw:page-thumbnail>
<draw:frame>
<draw:measure>
<draw:caption>
<draw:connector>
<draw:control>
<dr3d:scene>
<draw-custom-shape>


In the ODF 1.0 specification, draw:name is defined for all these shapes except <dr3d:scene> yet it is provided and assignable for both IBM Workplace and Open Office 2.0 for presentations (Impress). However, the name attribute does not appear in the ODF specification for <dr3d:scene>. It may mean that common-draw-shape-with-text-and-styles-attlist needs to be added to its attribute list. This oversight needs to be corrected.

Text should be added to these elements as follows:

for the name attribute,

draw:name is used as a short accessible name for alternative text. When transcoding from another document format to ODF the alt text shall be mapped to the draw:name attribute.

<svg:desc> Is used for the long description in support of accessibility.
Note: when transcoding from another document format to ODF the alt text shall be mapped to the draw:name attribute.

User agents supporting platform accessibility APIs should follow the following conventions for supporting the accessible name, accessible description (accessible help on Windows systems), and describedBy relationships:

If a draw:name is provided it should map to the accessible name. If not, the name should use the text referenced the text element identified by the draw:describedby attribute. <svg:desc> must be used to support the accessible description. User agents shall not manufacture names for the draw:name property, such as using the drawing object followed by a cardinal number in a string as draw:name is used for accessibility. Name assignments such as these provide no semantic meaning to the user.

Guidance for authors:
Authors should not assign names to objects having no semantic value. If no name is assigned the caption text will be used in its place. draw:name shall take precedence over the caption text for accessible name assignment by the user agent.

Assignment of the long description should only be necessary when a drawing object is significantly complex and the user needs more information to describe it. Long descriptions would be more applicable to drawing groupings than basic drawing shapes.


5.0 Establish clear relationship between a drawing objects and its caption by including a new optional draw:describedby attribute to the following drawing objects:

<draw-rect>
<draw:line>
<draw:polyline>
<draw:polygon>
<draw:regular-polygon>
<draw:path>
<draw:circle>
<draw:ellipse>
<draw:g>
<draw:page-thumbnail>
<draw:frame>
<draw:measure>
<draw:caption>
<draw:connector>
<draw:control>
<dr3d:scene>
<draw-custom-shape>
<dr3d:scene>

draw:describedby shall take a value of IDREF. The value for describedBy attribute shall be the target id assigned to the <text:sequence> used to represent the corresponding caption. As text:sequence is an XML element it may have an ID assigned by default. The following attribute list should be included as optional to the above drawing objects:

<define name="common-draw-describedby-attlist" combine="interleave">
<attribute name="draw:desribedby">
<ref name="IDREF"/>
</attribute>
   </define>

   When a caption is assigned by a user agent, an id must be assigned to the element containing the text used to caption a drawing element. The drawing element being captioned must then be assigned the draw:describedby attribute with an IDEF equivalent to the id of the captioning text thus establishing a relationship between the captioned text and the object captioned as needed for accessibility. Removing the caption should result in removing the describedBy attribute of the object that was being captioned.

If the user agent supports a platform which provides a ddescribedby relationship in its accessibility API, this relationship for captions should be used to fulfill the relationship.


Rich Schwerdtfeger
Distinguished Engineer, SWG Accessibility Architect/Strategist
Chair, IBM Accessibility Architecture Review Board
blog: http://www-106.ibm.com/developerworks/blogs/dw_blog.jspa?blog=441

"Two roads diverged in a wood, and I -
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