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'alt' was: SVGAccessibilityWG: has-been-clicked or a:visited

From: Jonathan Chetwynd <j.chetwynd@btinternet.com>
Date: Wed, 10 Nov 2004 20:14:52 +0000
Message-Id: <2E4E5803-3355-11D9-869F-000A95C7D298@btinternet.com>
Cc: www-svg@w3.org
To: Philippe Lhoste <PhiLho@GMX.net>

Philippe

We are not alone, alt and title have been used within html for some 
time, and whilst there are spec definitions* the practicality is that 
most implementors haven't got a clue.
It's worth realising just how simple things have to be, if we would 
like them to be useful.

in my own words: title is used to describe the destination of a link, 
alt is used to describe an image.
in this way you can see that where a graphic is also a link, both alt 
and title are 'essential' for accessibility.

Please note well, that while alt is  used for missing or broken links 
to images, it is also used by viewers such as lynx that cannot display 
images.

regards

Jonathan Chetwynd
http://www.peepo.co.uk     "It's easy to use"
irc://freenode/accessibility

*2 specs:

http://www.w3.org/TR/html4/struct/objects.html#adef-alt
alt is for user agents that cannot display images, forms, or applets, 
this attribute specifies alternate text.

http://www.w3.org/TR/html4/struct/links.html#h-12.1.4
The title attribute may be set for both A and LINK to add information 
about the nature of a link. This information may be spoken by a user 
agent, rendered as a tool tip, cause a change in cursor image, etc.

<BODY>
...some text...
<P>You'll find a lot more in <A href="chapter2.html"
        title="Go to chapter two">chapter two</A>.
<A href="./chapter2.html"
        title="Get chapter two.">chapter two</A>.
See also this <A href="../images/forest.gif"
        title="GIF image of enchanted forest">map of
the enchanted forest.</A>
</BODY>

On 9 Nov 2004, at 23:39, Philippe Lhoste wrote:


Will Pearson wrote:
> However, I don't know whether SVG is truely accessible to some users.  
> The
> problem comes down to how the semantic meaning encoded within diagrams 
> is
> visually extracted.  It isn't a problem unique to SVG, but a problem 
> with
> diagrams in general.  The technique of providing a textual equivalent 
> for
> elements of a drawing is fine up to a point, but problems arise due to 
> other
> semantic encoding techniques being used within diagrams.  Spatial
> relationships between diagram elements, colors, etc. can provide as 
> much
> meaning as the lines themselves do, and this is often either not 
> conveyed or
> not conveyed with any clarity by textual descriptions for a single 
> diagram
> element without the context of other diagram elements.  Therefore, 
> having
> things like LongDesc assigned to a <LINE> tag really don't make a 
> drawing
> 100% accessible to someone who has no means of extracting the meaning
> visually.

Some (general) remarks and various thoughts by somebody not in the 
accessibility "business" but interested by the issues:

- Accessibility isn't just about people with trouble with reading or 
viewing. Problem which you address correctly by using "to some users". 
Some parts of the art may be perceived, but can be hard to distinguish. 
So textual equivalent are only part of the accessibility, of course.

- Ultimately, an accessible viewer would read the SVG code... That's 
the advantage of SVG over bitmap images, they have semantics. Without 
going so far, it could be interesting to hover over a line (or any 
other shape) and extract some information, like exact color (named one 
even if #hhh is used) or thickness. Since these data can be used to 
convey information, like you mention, it could be a useful feature. Of 
course, for drawings conveying some information, like diagrams. It 
would be less useful for artistic drawings.

- I remember having seen a mouse with "force feedback", ie. that 
provide feedback on the environment where the cursor goes. To transpose 
examples to SVG, it would tickle when going over a stroke, or go 
sluggish over a given color. I wonder if this mouse is still sold.

Jonathan wrote:
 > To raise another issue,
 >
 >     It isn't clear why alt isn't included as well as title, they have
 > different functions perhaps one describing the image, and the other
 > the linked resource, surely essential accessibility for SVG?

I am not sure about what you are saying here. AFAIK, alt is used only 
in img tags (OK, area and input too). alt is here to provide a short 
description, in case of text-only browsers (or editors showing raw 
HTML...), or graphical browsers with images disabled, or even when the 
link to the image is broken.
It doesn't make much sense in SVG where the images are part of the 
document, so are not likely to be absent or not displayed. Of course, 
there is the image element which refers to external images, and where 
links can be broken, but it is not obvious how to use such alt 
attribute (if displayed inside the drawing, it can break it more than 
the current behavior of just ignoring the element with broken link).

-- 
Philippe Lhoste
--  (near) Paris -- France
--  Professional programmer and amateur artist
--  http://Phi.Lho.free.fr
--  --  --  --  --  --  --  --  --  --  --  --  --  --
Received on Wednesday, 10 November 2004 20:15:25 UTC

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