View source for PF/XTech/HTML5/DescriptorRequirements

= Providing Human-Parseable and Machine-Processible Terse Textual Alternatives and Markers for Static Images =

'''''NOTE: This document became obsolete on 4 March 2009; please [[PF/XTech/HTML5/TextAlternativeProposal| consult the 4 March collaborative edits to the most current proposal]]'''''

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== Recommended Usage ==

# null <code><nowiki>alt</nowiki></code> values '''MAY''' be provided '''ONLY''' if <code><nowiki>role="presentation"</nowiki></code>
# an image with an <code><nowiki>role="image"</nowiki></code> '''MUST''' be assigned a valid, meaningful, and human-parseable <code><nowiki>alt</nowiki></code> text
# when using <code><nowiki>IMG</nowiki></code>, <code><nowiki>role="image"</nowiki></code> '''SHOULD''' be the ''default value'', auto-inserted or manually inserted by the author; if the author changes that value from <code><nowiki>role="image"</nowiki></code> to <code><nowiki>role="presentation"</nowiki></code>, then the author must also provide a meaningful, human-parseable textual equivalent using the <code><nowiki>alt</nowiki></code> attribute for the source code to validate.

'''Note:''' We need to state normatively that <code><nowiki>alt</nowiki></code> text and the contents of the <code><nowiki>LEGEND</nowiki></code> child element, if <code><nowiki>FIGURE</nowiki></code> is used, should be identical, with the exception that the <code><nowiki>LEGEND</nowiki></code> text can be "rich" (contain markup); likewise, it is important to emphasize 

== Authoring Scenarios ==

'''''Note:''''' The code examples provided below are examples of code as might be output by an author or authoring tool or aggregator, such as Flickr.

=== Case 1: Image Needs alt, Author Provides It ===

'''Author's Source Code:'''

<pre><nowiki> 
<img src="123.jpg" alt="Photo of my granny"> 
 </nowiki></pre>


'''Commentary:'''
The act of populating the value for alt should trigger the insertion of <code><nowiki>role="image"</nowiki></code>, unless the use case is a composite image, in which case the composite should be contained in a <code><nowiki>DIV</nowiki></code> marked with <code><nowiki>role="image"</nowiki></code>, the <code><nowiki>alt</nowiki></code> text defined for the composite image '''MAY''' be contained in the first of the composite images, allowing the author to use <code><nowiki>alt=""</nowiki></code> on all of the other pieces of the composite image, provided that the first image contained in the composite describes the composite image fully. Authors '''SHOULD''' not break up the <code><nowiki>alt</nowiki></code> text if delivering an image in pieces -- attach it to the first piece of the composite. 

=== Case 2: Author Specifies the Image Should be Ignored ===

'''Author's Source Code:'''

<pre><nowiki> 
<img src="123.jpg" role="presentation" alt=""> 
 </nowiki></pre>


=== Case 3: Image Needs alt, Author Can't/Won't Provide It, Also Doesn't Care If Code is Valid ===

'''Author's Source Code:'''

<pre><nowiki> 
<img src="123.jpg"> 
 </nowiki></pre>


'''Commentary:'''
If the author uses <code><nowiki><img src="123.jpg"></nowiki></code>, the authoring tool or rendering engine should detect the missing alt attribute and insert a <code><nowiki>type="invalid"</nowiki></code> or <code><nowiki>type="incomplete"</nowiki></code> or, more practically, the <code><nowiki>role="image"</nowiki></code> to denote that this is visual content which '''MUST''' have a textual alternative provided for it 

=== Case 4: Image needs alt, author can't/won't provide it, but does want code to be valid ===

'''Author's Source Code:'''

<pre><nowiki> 
<img src="123.jpg" alt=""> 
 </nowiki></pre>


'''Commentary:'''
Without the <code><nowiki>role="presentation"</nowiki></code> this case should be flagged as a failure/error -- the author hasn't provided the requisite information that declaratively marks the image as presentational, so the empty value for <code><nowiki>alt</nowiki></code> should be flagged as an error, with the fix being: 

* if <code><nowiki>role="presentation"</nowiki></code> is not present, this is invalid markup; validation engines should report this as an error and advise the author to use the <code><nowiki>role="presentation"</nowiki></code> to the image, provided that the image is purely decorative and devoid of content; authors should also be advised that they must use <code><nowiki>role="presentation"</nowiki></code> to validate their source code. <code><nowiki>alt=""</nowiki></code> is allowed '''ONLY''' when <code><nowiki>role="presentation"</nowiki></code>. 
* if <code><nowiki>role="image"</nowiki></code> is present, and no value has been defined for the <code><nowiki>alt</nowiki></code> text, that should be flagged as invalid; author should be prompted to provide a programmatically determinable textual equivalent using the <code><nowiki>alt</nowiki></code> attribute, whose value should be identical to that provided by the <code><nowiki>LEGEND</nowiki></code> element if the <code><nowiki>IMG</nowiki></code> is contained in the <code><nowiki>FIGURE</nowiki></code> element; 

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== Conclusions So Far ==

# null <code><nowiki>alt</nowiki></code> values '''MAY''' be provided '''ONLY''' if <code><nowiki>role="presentation"</nowiki></code>
# an image with an <code><nowiki>role="image"</nowiki></code> '''MUST''' be assigned a valid, meaningful, and human-parseable <code><nowiki>alt</nowiki></code> text (again, we need to reinforce that <code><nowiki>alt</nowiki></code> text and the contents of the <code><nowiki>LEGEND</nowiki></code> child element, if <code><nowiki>FIGURE</nowiki></code> is used should be identical, with the exception that the <code><nowiki>LEGEND</nowiki></code> text can be "rich" (contain markup)
# when using <code><nowiki>IMG</nowiki></code>, <code><nowiki>role="image"</nowiki></code> '''SHOULD''' be the default value, auto-inserted or manually inserted by the author; if the author changes that value from <code><nowiki>role="image"</nowiki></code> to <code><nowiki>role="presentation"</nowiki></code>, then the author must also provide a meaningful, human-parseable textual equivalent using the <code><nowiki>alt</nowiki></code> attribute 

== Related Resources ==

* [[AlternateProposal| Alternate Proposal from GreggV]]
* [[PF/XTech/HTML5/DescriptorRequirements-v2|Proposal| GreggV+GJR]]]
* [[PF/XTech/HTML5/RoleAttribute| A role Attribute for HTML5]]
* [[PF/XTech/HTML5/MediaSpecificElements| A Unified Approach to HTML5's Media Specific Elements]]

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* [[PF/XTech/HTML5| PF XTech HTML5 Issues & Requirements Index]]
* [[PF/XTech| XTech Wiki: Cross-Working Group Issues Index]]
* [http://www.w3.org/WAI/PF/group Protocols & Formats (member start page)]