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Re: feedback requested on WAI CG Consensus Resolutions on Text alternatives in HTML 5 document

From: Leif Halvard Silli <lhs@malform.no>
Date: Sun, 16 Aug 2009 23:11:38 +0200
Message-ID: <4A88760A.3070306@malform.no>
To: Henri Sivonen <hsivonen@iki.fi>
CC: Sam Ruby <rubys@intertwingly.net>, Steven Faulkner <faulkner.steve@gmail.com>, Ian Hickson <ian@hixie.ch>, HTMLWG WG <public-html@w3.org>, W3C WAI-XTECH <wai-xtech@w3.org>
Henri Sivonen On 09-08-16 18.03:

> On Aug 16, 2009, at 17:51, Sam Ruby wrote:

> Based on what I gather from comments praising Dreamweaver and 
> from my own reasoning, I think the advice at step #2 should be 
> that an authoring application in the situation where its user 
> doesn't supply a text alternative must not generate a text 
> alternative (especially not from the file name) and must not 
> generate markup that masks the existence of the image (empty 
> alt or role=presentation). Therefore, an image tag without an 
> alt attribute or a role attribute should be generated when the 
> user of the authoring application hasn't affirmatively provided
>  a text alternative or an assertion of presentationality.

I agree that it should not insert role="presentation" by default. 
However, since we both agree with Consensus in that <img> without 
@role defaults to role="img", it could insert role="img". Lack of 
@role would not be signal of lack of role ...

Tools do not need to ask "Do you want to insert an <img>?" They 
could offer choice between IMG@role=presentation and normal IMG. 
Tools should not bug users about lack of alternative text unless 
the <img> has  a non-presentational role ... That <img> defaults 
to role="img" makes not sense for authoring unless the 
requirements for role="img" follows by.

The real question here is the role and use of empty alt="". I 
agree with you that the tool should not automatically insert an 
empty alt. But we may not agree about why. A tool should not 
automatically assume that an IMG with empty alt="" is equal to a 
IMG with role="presentation", but ask the author for confirmation.

> As a matter of language design, I think the absence of the alt

> attribute is a sufficient syntactic signal of its absence.


The disagreeable point is/has been whether lack of textual 
alternative  has any meaning other than "<IMG> with an absent text 
alternative". Another disagreeable point is whether such a thing 
automatically should trigger an error message.

> I think adding more syntax for affirming its absence (e.g. 

> noalt, missing, etc.) is unhelpful.


Agree.

We should treat lack of @alt and empty alt="" as semantically 
identical. The Consensus Documents goes in that direction when it 
states that it doesn't mater if an <IMG> with role="presentation" 
has an empty alt="" or no alt at all. But it goes slightly in the 
opposite direction when it recommends that validators should say 
that an <IMG> with an empty alt="" but not @role should 
automatically get a role="presentation". A tool might have its 
internal semantics where empty alt="" is equal to 
role="presentation". But a validator should not derive any role 
from the fact that @alt is either omitted or empty. It may 
/assume/ a role, perhaps ...

I think it is important that we do not let @alt and @role eat into 
each others roles. It must be clear that @role comes first and 
@alt comes second. The @alt content depends on @role and not the 
opposite.

Thus it is problematic if one may change the role to 
"presentational" by adding an empty alt="" attribute.  Would we be 
able to change the role to "presentational" through the adding of 
an empty aria-labelledby="" attribute as well?

>> * Having @alt "required" in HTML 4.01 raised public awareness
>>  of Web accessibility in general.
> 
> Agreed, however, the requirement has also caused people to 
> write software that puts stuff specifically disapproved by ATAG
>  2 into alt just to satisfy validators.


Or may be those behavior problems are due to the lack of a 
<presentationalimage> element ...
-- 
leif halvard silli
Received on Sunday, 16 August 2009 21:12:24 UTC

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