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Bug 13115 - Confusing contradiction in description of "alt" attribute
Summary: Confusing contradiction in description of "alt" attribute
Alias: None
Product: HTML WG
Classification: Unclassified
Component: LC1 HTML5 spec (show other bugs)
Version: unspecified
Hardware: PC Windows NT
: P2 normal
Target Milestone: ---
Assignee: Ian 'Hixie' Hickson
QA Contact: HTML WG Bugzilla archive list
Keywords: a11y, a11y_text-alt
Depends on:
Reported: 2011-07-01 17:15 UTC by html5bugs
Modified: 2012-01-10 19:08 UTC (History)
7 users (show)

See Also:


Description html5bugs 2011-07-01 17:15:51 UTC
Some thoughts about

I noticed that it contains a main paragraph which attempts to summarize the intent and purpose of alternative text for images. I do not believe that the intent and purpose of alternative text can be summarized in a general rule or guideline, but rather that they must be understood in both a positive and negative sense for proper use: to provide data meaningful for something or someone who does not see the image, but also NOT to provide data that could be meaningful for someone who can see the image. 

> "The most general rule to consider when writing alternative text is the following: the intent is that replacing every image with the text of its alt attribute _not change the meaning of the page_."

My stress is on the phrase _not change the meaning of the page_

It is clear that replacing every image with the text of its alt attribute changes the meaning of the page in the majority of instance, unless one supposes that images have no meaning.

Rather than making one contradictory generalization like this, it would be more helpful to web authors to divide this "purpose of alternative text" into two complementary guidelines:

* Alternative text should provide information that is meaningful and useful to something or someone who CANNOT see the image. This data should be adequate (as far as possible) to take the place of the image and should at least indicate the role or appearance of the image.

* Alternative text should not provide any information that adds meaning beyond the image itself to someone who CAN see the image. Titles, captions, and any other data regarding the photograph that are meaningful to someone viewing the photograph should be provided by a method other than alternative text.

(All-CAPS words can be replaced by bold / strongly-emphasized test.)

As you have done, examples and other notes can be added as needed after the main guidelines for alternative text. A few such that I believe are helpful to communicate the sense of distinguishing between alternative text and title text, etc.:

+ "blonde bombshell" should not be used as the alternative text. Blonde alone would be fine because this carries no further meaning useful to someone who can see the photograph, but it does carry meaning for a search engine or person unable to see the photograph. However, when "bombshell" is added to the phrase, then both words "blonde bombshell" should be moved to another attribute of the image, such as its title, or or some page element nearby, but outside of the image itself. (Another copy of the word "blonde," by itself, could still be provided in the alternative text.)

+ A person's name should not be used in the alternative text--even though this may be of value to search engines, it is of value also to those who may be seeing the photograph and do not know the subject's name. A search engine should consider words in both the alternative text, the title, etc., when trying to find descriptive keywords for the image.

+ It will be clear to a user that the alternative text is taking the place of an image, so the alternative text should not provide redundant or pseudo-graphical information like "[image: blue border]"--in this case the brackets are useless graphical formatting / ASCII art (the purpose of alt text is not to provide another form of an image), and the "image:" prefix indicating the presence of an unseen image is redundant.

+ In a nutshell, the alternate text will NOT BE SEEN by anyone who is viewing the images, and so important information like photo dates, locations, and any data that is still meaningful for someone viewing the image should NOT be contained in the alternative text.

This last point is already a part of the two complementary positive and negative guidelines for alternative text, but I think it bears repeating and needs to be made especially clear. So often alt tags contain information that should be in other tags, and vice versa.

You can do a lot better job, I'm sure, writing this up for the specification than I can. But I think that this way of thinking of alternative text as a positive and negative set of guidelines is a worthwhile idea.

Just saying that "replacing images with alt should not change the meaning of the page" is not going to be enough to help people understand what to put in alternative text, and what NOT to put in alternative text.
Comment 1 Ian 'Hixie' Hickson 2011-09-23 23:17:54 UTC
This section is followed by _thirteen_ sections, some rather long, giving more detail. Is this not sufficient?

I disagree that the general advice is wrong. It is true that alt="" is supposed to provide text that is equivalent to the meaning (it's an "alternative" to the image). That's the whole point.
Comment 2 Ian 'Hixie' Hickson 2011-09-26 22:28:22 UTC
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Status: Did Not Understand Request
Change Description: no spec change
Rationale: see comment 1