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Re: ISSUE-30 (Longdesc) Change Proposal

From: Jonas Sicking <jonas@sicking.cc>
Date: Thu, 29 Oct 2009 14:47:52 -0700
Message-ID: <63df84f0910291447o2ff39440y43223d78d025374d@mail.gmail.com>
To: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Cc: Charles McCathieNevile <chaals@opera.com>, "public-html@w3.org" <public-html@w3.org>
On Thu, Oct 29, 2009 at 2:15 AM, Leif Halvard Silli
<xn--mlform-iua@xn--mlform-iua.no> wrote:
>> And regarding descriptions:
>>
>> "a description is intended to provide detail that some users
>> might need"
>>
>> However neither seems to describe @alt. Both the HTML4 spec,
>> and the implementations I know, treat @alt as fallback content:
>>
>> "alternate text to serve as content when the element cannot be rendered
>> normally"
>
> I take it that in your view neither aria-label, aria-labelledby nor
> aria-describedby represent a [near] duplicate feature of @alt.

I don't really think it matters, given that I think we all agree on
what should happen regarding @alt. I.e. that it should not be removed
from the spec.

But if it matters what I think regarding it's [near] duplicity: I do
think that @alt seems intended to be used different from
@aria-label/@aria-labelledby/@aria-describedby. However in practice I
think you'll find a significant amount of @alt attributes actually
containing information that is a description rather than fallback. In
fact, I suspect there is more such usage of @alt, than fallback usage
of @alt. But I don't have data either way.

>> The same can not be said for @longdesc and @summary, neither of
>> which has seen any significant amount of real-world uptake.
>> Yes, there is more than zero uptake, but I don't think there is
>> enough to warrant having duplicate (or near-duplicate)
>> features.
>
>
> Above you lead us to see that the neither aria-label, aria-labelledby nor
> aria-describedby are fallback, and thus are not [near] duplicate features of
> alt.
>
> In my previous reply, I gave you the spec definition of @longdesc that you
> asked for: It is a long variant of alt. Thus it is fallback.
>
> Therefore I am baffled that you bring up "duplicate feature" again.

Ah, I think I missed to reply to this argument before.

What do you have to back up the claim that @longdesc is fallback?

I did some research for this statement and here is what I found.

Support from specs:

The DTD from the HTML4 spec says for @alt

"short description"

and for @longdesc

"link to long description (complements alt)"

So here it seems to indicate that both are descriptions, and that
@longdesc is a longer version of @alt. Note that I don't think that
you can infer from "complements alt" part that the two have similar
functionality.

However, if you look at the actual descriptions of the two attributes,
it says that about @longdesc

"This attribute specifies a link to a long description of the image"

So far this matches the DTD. However for @alt it says

"For user agents that cannot display images, forms, or applets, this
attribute specifies alternate text".

I.e. here it seems to talk about @alt as fallback.

So it seems to me that the HTML4 spec is internally inconsistent, or
uses different terminology from ARIA. I.e. possibly it treats
"description" and "alternative text" as the same thing.

So there's two ways where I can see that you could argue that HTML4
defines @longdesc as fallback:

1. If you read the part where it says that @alt is fallback. And also
read the part where it says that @longdesc is a longer description and
@alt is a short description, and look at the fact that that would make
@longdesc a longer version of @alt, but ignore the fact that it says
that both are descriptions.
2. If you argue that everywhere where HTML4 says "description" it
means "alternative text" and thus "fallback".


Support from implementations:

I can't find any implementations that treat @longdesc as fallback. No
browser that I know of displays the contents of the uri that @longdesc
points to when you turn off images. None even displayed a link or the
@longdesc uri.

However I only checked a few popular browsers. Does anyone know any
implementations that treat @longdesc as fallback


Support from the actual change proposal from Charles:

It appears clear to me that Charles is proposing @longdesc to be a
description, not fallback. Quoting from his change proposal:

4.8.2.1.1, 4.8.2.1.2, 4.8.2.1.3 should all mention that a longdesc
*may* be provided to provide a detailed *description* of the image,
e.g. to help a person who cannot see it to find it from a description.

(emphasis is part of the actual change proposal).


All in all I could not find a good case for @longdesc being fallback
rather than a description. The best case was the HTML4 spec, where you
had to either use extremely selective reading, or had to assume that
it was confusing terms.


However, ultimately, if you think that @longdesc should be used to
indicate fallback I suggest that you make a Change Proposal to that
effect. It does not appear that this is what Charles is proposing.

/ Jonas
Received on Thursday, 29 October 2009 21:48:52 GMT

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