From HTML WG Wiki
Mint a new attribute for relaxing alt attribute conformance criteria in certain situations
To enable large Web applications to effectively monitor their own markup quality, without enroaching on markup generators' existing efforts to market their tools, we should mint a new
relaxed="" attribute for
<img> elements which allows for the granular relaxation of certain author conformance requirements.
This is for ISSUE-206 meta-generator.
The spec currently allows conformance checkers to waive
alt="" conformance requirements on pages with
<meta name=generator> present. This feature is intended to allow sites like Flickr (which accept bulk photo uploads from their users and can't reasonably require their users to provide alternative text) to check the conformance of their Web applications without being inundated with warnings or errors that the site developers can't do anything about. If we don't allow such sites to do this, they have and will add bogus
alt="" text to their pages simply to pass in popular conformance checkers, thus harming the accessibility of their pages.
This is an important use case to address, but there are two problems with this feature as currently specified:
<meta name=generator> feature has been present in HTML for many years; in 1997, 7.5% of web pages had
<meta name=generator> specified.  In all that time,
<meta name=generator> has had no effect on the criteria used when checking the conformance of web pages containing it. Most if not all tools which emit
<meta name=generator> have not intended to affect the conformance of documents by doing so—they simply emit
<meta name=generator> as a means of marketing their tools to potential users.
Authors or mantainers of popular tools such as Blue Griffon and HTML Tidy have expressed a) that they will not stop emitting
<meta name=generator>, and b) that their users do not expect
alt="" conformance requirements to be relaxed on content generated with these tools.  
<meta name=generator> exception is document-wide. The markup of large Web applications is typically partly generated from code and partly sourced from hand-authored HTML templates. With an all-or-nothing mechanism, there's no way to relax the conformance criteria for only the portions of the document corresponding to user-generated content, while retaining strict requirements on the portions of markup from the hand-authored HTML templates.
Given these deficiencies, this Change Proposal proposes to address the given use case with a granular mechanism that does not overlap with an already-existing markup practice.
In §4.8.1 "The img element," add a
relaxed="" boolean attribute to the
<img> element. Define the attribute like so:
relaxed=""attribute indicates by its presence that the
<img>element's content was provided by a different author than that of the embedding document.
In §126.96.36.199.12 "Guidance for markup generators," add the following paragraph after the paragraph which begins with "As a last resort…":
Generators may mark
alt=""attributes with the
relaxed=""attribute when the
<img>element's lack of alternative text should not affect the conformance of the rest of the document.
In §188.8.131.52.13 "Guidance for conformance checkers," replace the second bullet (which starts with "The document has a meta element…" with the following text:
<img>element has a
relaxed=""attribute specified. Conformance checkers may choose to report this error; for example, there could be a user option to report conformance errors for this case.
- We no longer imbue
<meta name=generator>with effects incompatible with its historical and deployed usage;
- We enable engineers of large Web applications to catch markup errors that they can do something about, without bothering them about markup errors they can't do anything about.
Conformance Classes Changes
- This change alters the following conformance classes:
- Conforming documents,
- Conformance checkers, and
- Authoring tools and markup checkers.
- Authors may simply add
relaxed=""to all of their
<img>elements to avoid authoring good alternative text.
References are linked inline.
- Edward O'Connor