[Bug 13115] New: Confusing contradiction in description of "alt" attribute

http://www.w3.org/Bugs/Public/show_bug.cgi?id=13115

           Summary: Confusing contradiction in description of "alt"
                    attribute
           Product: HTML WG
           Version: unspecified
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: normal
          Priority: P2
         Component: HTML5 spec author view
        AssignedTo: mike@w3.org
        ReportedBy: html5bugs@gmail.com
         QAContact: public-html-bugzilla@w3.org
                CC: public-html-wg-issue-tracking@w3.org,
                    public-html@w3.org


Some thoughts about

4.8.1.1.1

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.

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Received on Friday, 1 July 2011 17:15:56 UTC