Why the Alt Attribute May Be Omitted. “The benefit of requiring the alt attribute to be omitted, rather than simply requiring the empty value, is that it makes a clear distinction between an image that has no alternate text (such as an iconic or graphical representation of the surrounding text) and an image that is a critical part of the content, but for which not alt text is available.”
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however, it doesn't cater for the third scenario: an image that is indeed a critical part of the content, but for which the author - through negligence, ignorance, or non ATAG-compliant authoring environments - has not provided an alternative. being able to distinguish between images that are simply iconic/representative of surrounding text and those that have not been authored correctly is essential for signalling to assistive technology whether or not it should attempt heuristics (reading filename, for instance) or alert the user (by simply announcing "image") in the latter case.
patrick h. lauke - 25th August 2007 16:06 - #
Actually it does cater for that case -- basically any image without an "alt" is "not authored correctly". The spec even explicitly says that UAs should enable heuristics in that case. The spec just says to _not_ use alt="" if you know you _should_ include alt text but haven't.
Ian Hickson - 26th August 2007 09:26 - #
so how do you distinguish between "not authored correctly" and "icon or graphical representation of the surrounding text"?
patrick h. lauke - 26th August 2007 12:01 - #
An image that is an "icon or graphical representation of the surrounding text" has an empty alt="" attribute.
Is this not clear in the spec?
Ian Hickson - 26th August 2007 21:22 - #
What's the difference between "not authored correctly" and "invalid"? Why should the spec be changed to make something authored incorrectly valid when it's previously been invalid?
Jim - 28th August 2007 11:11 - #
There's no difference between "not authored correctly" and "invalid". They are both just informal ways of saying "not conforming to the HTML5 specification".
Ian Hickson - 4th September 2007 07:08 - #
Ian, please give us three examples, fully functional on public Web sites, which, in conjunction with shipping versions of adaptive technology, have enough "heuristics" to "enable" in order to completely make an image with an alt text understandable to a blind person.
Joe Clark - 14th September 2007 21:56 - #
I don't understand the question. Are you asking for examples of images that have correct alt="" text?
Ian Hickson - 18th September 2007 03:05 - #