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ALT Text Notes and Guidelines (take 2)

From: Gregg Vanderheiden <po@trace.wisc.edu>
Date: Thu, 17 Jul 1997 00:57:42 -0500
Message-ID: <01BC924C.6FFC3260@1Cust80.Max4.Portland2.OR.MS.UU.NET>
To: "'w3c-wai-wg@w3.org'" <w3c-wai-wg@w3.org>, "'Uaccess-L'" <uaccess-l@trace.wisc.edu>, "Webwatch-L (E-mail)" <webwatch-l@teleport.com>
Here is an attempt to capture some of the comments made on this recently.

This is still rough but perhaps less so than last time.

Comments welcome 

Gregg






TYPES OF GRAPHIC USE (SIMPLE MODEL)
Remember it is not what the graphic is but how it is used that determines which category it falls in.  (These categories are NOT necessarily EXCLUSIVE)


1)  as DECORATION -  Something with no particular information value in understanding the intent and content of the page but which someone may want to know the description of.   
        Example: a decorative picture, a colored bar at the top of a page, something to make layout prettier but which does not provide document organizational information, etc may fall in this category.  


2)  as LABEL/TITLE/STRUCTURE - a picture which does nothing (not a link) but serves as an identifier, a label, a title or some other information that is important to understanding the organization or purpose of the page or section of the page
       Examples:  


3)  as GRAPHIC PRESENTATION OF INFORMATION - this is information which is presented in graphic form.  Much more than a title, it would require multiple sentences to convey the information that is presented in this image.  And the information is not casual information (e.g. a logo showing people surrounding a world), but information which is central to understanding the information presented on the page.  
        Examples:  A chart or diagram.


 4)  as ANCHOR - a graphic that is serving in place of anchor text for a link.  These anchors graphics sometimes ALSO serve functions 1, 2 , or 3 in addition to being an anchor.   [ Note: anchors are different from Uses 1,2,and 3 in that they exist in their own context and information about  the anchor target for instance could be conveyed within the <A> itself rather than in the graphics context (e.g. using TITLE, or REL) ]


NOTE: Animated graphics would be handled in the same manner as other graphics unless they are long enough to constitute a movie.  Then they should have time synched descriptions.





ROUGH DRAFT SET OF COOPERATIVE ACCESS GUIDELINES (FOR BOTH WEB PAGE CREATORS AND BROWSER DESIGNERS)

PAGE CREATOR GUIDELINES

P1)  ALT TEXT 
     All images should have an ALT tag that would tell you the FUNCTION of the graphic.  
       Examples:  "IBM Logo",  "Section Title: Banana Products",  "Graph of population vs age",  "Divider Line", "bullet" (though some say a bullet should just have an * for the alt text), "More Information", "Search Button"
       Note: There is not a consensus on whether ALT="" should be used.  It works well for some browsers such as Lynx but not for others like Netscape or IE where it just behaves just like no alt text leaving an unexplained graphic symbol on the page. 


P2) TEXT DESCRIPTION
All images should have a SEPARATE TEXT DESCRIPTION.  This is in addition to, and separate from, the Alt text.  This text description of the graphic can be stored in one (or more) of the following places:
        1) The descriptive text can be stored on a separate html page.  A link to the description can be placed next to the image.  It is suggested that a Capital D be used as the anchor text for the link to this text.  (this technique is known as the D-Tag or D-Link technique.  [Notes: It works today.  It works with all browsers. Some view this as a temporary technique until other techniques such as those listed below are implemented and supported by browsers]
        2) The descriptive text could be stored in a PARALLEL FILE that is stored separately from the graphic file.  An ALTSRC= tag could be used to indicate that there was a description file. The file could have any name or location.   [Notes: This technique requires that the browser support the ALTSRC feature.  The browser would provide some indication to the user that there was a description available for this graphic.  Perhaps a distinctive character could be added to the end of the alt text like a "+".]
        3) The description could be included as part of the graphic file if the graphic file format supports this.  PNG for example does.  [Notes: This technique requires the use of PNG or other graphic file format that supports text. It also requires the browser to support the technique (as in strategy #2).  It can be used in conjunction with strategy two.] [It would be best if there were a way for the user to request the text portion of a PNG file without downloading the full graphic file]
	[General Note:  Strategy 2 seems to be the most flexible.  It works with all graphic formats.  It is similar in structure the format suggested for audio files]

P3) DESCRIPTION OF VIDEO OR ANIMATION
All video sequences should be accompanied by an auxiliary audio track which includes a description of the important aspects of the video presentation.  If the video player allows mixing of audio then the track could be mixed with the regular audio track.  If mixing is not provided then the auxiliary audio track should include both the description and the regular audio track. 
       NOTE: not all video or animation formats have audio.  Not all allow multiple audio tracks.  An interesting thought would be to support parallel audio track that could be merged and time synched with a video or animation when it is played.   This would be similar to the strategy being suggested for captioning.




BROWSER DESIGN GUIDELINES

B1) UNDERLINE ALT TEXT IF IT IS AN ANCHOR
if an image is an anchor then the browser should underline the ALT TEXT and color it just like it does any text anchor.  (Otherwise there is no way to tell a passive-graphic from a graphic-link.)

B2) INDICATE AND PULL UP LONG DESCRIPTIONS OF GRAPHICS ON COMMAND
All browser should have a command that could be issued (while the user is on a graphic), to cause the long text description file (see P2 above) to be fetched and put into the displayed document at the location of the Graphic (with square brackets around it).  If there was not a long description available for the graphic then the browser would signal the user (beep?).
        NOTE: the command would have to be something that was easily accomplished with a screen reader. - Perhaps an "Alt Click" or "Control Click" on the alt text.   


B99) OPTION TO SUPPRESS DECORATIVE GRAPHICS
There could be a user option which would tell the browser to suppress (or not show) images that are marked as decorative only.   
        Note:  I'll suggest this here for discussion, but I think that it may be asking for something which is not a very big problem.   It adds to browser complexity.  And decorative graphics make up only small part of pages.  If they are properly labeled with short alt text they can be quickly skipped over.   Most page designers are likely to label only a small number of graphics on their pages as purely decorative anyway.    This also requires that there be a way to specify that a graphic is decorative only... which is more work for page designers.   I think we should focus page designers on more central issues.   



I note that we have focussed on the Graphic only in this particular thread.  We need a similar set for Audio information.  I'll try that in a parallel memo to get ideas and input.


Gregg

-- ------------------------------
Gregg C. Vanderheiden Ph.D.
Professor - Dept of Industrial Engineering
Director - Trace R & D Center, Waisman Center
University of Wisconsin- Madison
gv@trace.wisc.edu,    WWW&FTP at  Trace.Wisc.Edu
for a list of our Listserves send "index" to listproc@trace.wisc.edu




 

Received on Thursday, 17 July 1997 01:58:47 EDT

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