Accessibility SC Proposal for alternative text

What follows is the latest version of the accessibility
subcommittee's proposal for extending alternative text support.  We
think this is pretty much our final word on this subject, but will discuss
it one final time at our face to face meeting May 20-21.  Meanwhile,
however, we wanted the whole TC to see what we're proposing.

Note in particular that in section 3.0 there is an
explicit reference to what Microsoft Office does.  The TC should decide
if it wants that language in the standard.

Please send any comments to .
 Thanks.  -- Nathaniel

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Executive Summary of proposed changes addressing alternative
text for non-

text elements and hypertext links:

An accessibility gap in the ODF specification is alternative text support

for non-text objects. Additionally, the specification does not allow for

"hint" text for hypertext links. These are 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. We had 

considered the use of draw:name and office:name (hyperlink) properties
for

alternative text however feedback from some TC members indicated that this

already had "legitimate uses and its reuse was inappropriate."

Subsequently, the subteam recommends the use of the <svg:title> element,

from SVG, for alternative text and

the <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:p>

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 <svg:title> element must be provided as an optional element to
the following:

draw:area-rectangle

draw:area-circle

draw:area-polygon

Text should be added to these elements as follows:

<svg:title> is used as a short accessible name. When transcoding
from 

another document format to ODF the short names, like HTML's alt text on

the <img> tags shall shall be mapped to the <svg:title> element.

Alternative in Microsoft Office is considered a short name and should be

mapped accordingly.

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

2.0 Drawing layer

The <svg:desc> element must be provided as an optional element to
the <draw:layer>

. This element must apply to all ODF document formats for which <draw:

layer> is used. 

Text should be added as follows:

<svg:title> is used as a short accessible name. When transcoding
from 

another document format to ODF the short names, like HTML's alt text on

the <img> tags shall shall be mapped to the <svg:title> element.

Alternative in Microsoft Office is considered a short name and should be

mapped accordingly.

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

3.0 Drawing shapes (line 5926 of spec.)

 

The <svg:title> and <svg:desc> elements must be provided as
an optional 

element to all drawing shape elements defined below for all ODF document

formats for which these drawing shapes 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>

Text should be added to these elements as follows:

<svg:title> is used as a short accessible name. When transcoding
from 

another document format to ODF the short names, like HTML's alt text on

the <img> tags shall shall be mapped to the <svg:title> element.

Alternative in Microsoft Office is considered a short name and should be

mapped accordingly.

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

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 an <svg:title> element 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 

<svg:title> element, such as using the drawing object followed by
a 

cardinal number in a string as it 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. <svg:title>

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.

Authoring tool responsibility for presenting and prompting for the <svg:title>
and 

<svg:desc>:

Authoring tools should provide an option from an objects context menu to

allow the user to enter the text for either of these elements as a 

minimum. More proactive authoring tools should have a facility for 

prompting the author for this text. Since <svg:desc> is a long 

escription, a text area vs. a text field should be used to prompt the 

user accordingly in GUI-based authoring tools like Workplace and Open Office.

Navigation tools, such as in Workplace and Open Office, used to list the

objects in the view should provide

the type of object followed by the contents of <svg:title>. The title
must

have been entered by the author.

For <draw:g> elements the drawing objects who are members of the
group 

should visible only when the group is expanded. 

4.0 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:measure>

<draw:caption>

<draw:connector>

<draw:control>

<dr3d:scene>

<draw-custom-shape>

<dr3d:scene>

<draw:frame>

draw:describedby shall take a value of IDREF. The value for describedBy

attribute shall be the target id assigned to the <text:p> used to

represent the corresponding caption. As text:p 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 describedby 

relationship in its accessibility API, this relationship for captions 

should be used to fulfill the relationship.

5.0 Establish text hints for hypertext links

The <svg:title> element must be provided as an optional element to
<text:a> 

<svg:title> is used as a short accessible description for hint text.
When 

transcoding from another document format to ODF the alt text, shall be

mapped to the <svg:title> element. When exporting ODF documents to
HTML, 

the contents of title text should be mapped to title attribute text on

HTML anchor tags. As a minimum, authoring tools should provide a mechanism

to provide the hint text. 

The title text should be made accessible to the assistive technology and

user. The user agent should allow for programmatic access through standard

accessibility APIs such as the accessible description. User should 

experience visible access to the hint text via the keyboard or mouse.

Appendix:  Proposed schema for svg-title

<define name="svg-title">

     <element name="svg:title">

         <text/>

     </element>

</define>

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