W3C home > Mailing lists > Public > public-html@w3.org > August 2007

Re: Distinguishing different aspects of accessibility (was Re: Marking up links to alternative versions of content)

From: Henri Sivonen <hsivonen@iki.fi>
Date: Fri, 3 Aug 2007 12:28:20 +0300
Message-Id: <C813D73E-06AE-4048-A835-EE027FA4DC26@iki.fi>
Cc: public-html@w3.org
To: Sander Tekelenburg <st@isoc.nl>

On Aug 2, 2007, at 19:20, Sander Tekelenburg wrote:

> However, a need to be able to access all equivalents is not the  
> same as a
> need to always have all equivalents presented.

If one wants to both have access to all versions available *and* not  
have them all offered up front, there needs to be a mechanism for  
indicating that there are other "equivalents" and a mechanism for  
bringing up a list of the other versions on request. Whether this is  
worth the trouble depends largely on how often users feel the need to  
inspect the list of alternatives anyway and how often authors would  
bother to produce markup in support of the mechanism.

> (When some equivalent cannot be consumed by a user, that equivalent  
> should not be forced upon the user --
> the user may have disabled sound or images, for instance.)

I'm not sure what you mean when you say "forced upon the user". If  
access to all equivalents is to be provided, surely at least an  
indicator of the presence of other alternatives needs to be presented  
to the user. Does that count as "forcing upon the user"?

As far as user needs go, if a user who is not deaf has disabled audio  
in order to avoid disturbing other people on mass transit or in a  
shared office, (s)he probably doesn't want the UA to hide indicators  
that audio exists (e.g. links to audio files), because the user could  
choose to plug in headphones or revisit later if the text pitching  
the audio content makes it seem interesting enough.

Do deaf users generally wish that UAs suppressed or compacted  
indicators of non-decorative (decorative being those marketing site  
background jingles) audio content availability? (This is an honest  
question. I don't know. But I can imagine that being aware of the  
availability of audio content could help establish context even if  
one couldn't listen to the audio. That is, would it be important to  
suppress or compact a link "Download podcast" if there was a link to  
transcript next to it?)

Likewise, users who aren't blind but have disabled images or Flash  
presentations in order to work around limitations imposed by the  
incumbent mobile operators don't want the existence of images or  
Flash presentations to be suppressed but instead want to be able to  
guess interestingness from the text context and be able to download  
visual content on a case-by-case basis.

Do blind users generally wish that UAs suppressed or compacted  
indicators of non-decorative visual content availability? (Again,  
this is an honest question. I don't know. But, again, I can imagine  
that being aware of what content was offered could help with  
establishing context.)

> In fact, for most users in most situations the ideal presentation  
> will be to be confronted with
> one equivalent.

Even if the users eventually wants to consume only one alternative,  
the hard part is making software make that choice *correctly* and so  
that the user has confidence in the software making the choice  
correctly. This involves having a DWIM engine.

> (A user wants to see a movie. Being forced to choose from  
> transcripts, captioned versions, Real, WM, QT, versions, etc. will  
> confuse many users.

How's the browser going to know that *this particular time* the users  
wants to see a movie instead of skimming the transcript? How's tho  
browser going to figure out that the user can listen to an English- 
language newscast without subtitles but needs some help with drama  
where the characters have a strong regional accent? How's the browser  
going to know that even though the platform has none of RealPlayer,  
Windows Media Player or QuickTime Player available, the user has  
installed a standalone contraband-in-the-U.S. app that can play  

> Therefore I'm saying that users should by default be confronted  
> with only one
> equivalent.
> [2] override that in iindividual cases

To me, that seems inherently complex.

>> Prose is human-to-human communication. What that prose says
>> communicates (dis)confidence about the nature of the alternative to
>> another human more effectively than a necessarily simplified machine-
>> readable markup assertion.
> I honestly cannot follow. A boolean leaves way less room for  
> misunderstanding
> than human language.

Suppose there are two files: PowerPoint and PDF. Also suppose the  
user has neither Windows nor PowerPoint but has OpenOffice.org and a  
PDF reader. Which downloadable is the user going to pick? Which one  
would the browser pick for the user?

Suppose there's fancy markup that says there are two files of a  
presentation titled Foo Bar in formats application/pdf and  
application/vnd.ms-powerpoint and browser UI that generates a  
presentation for this. Now, *if the browser can map the MIME-types to  
sensible human-readable strings*, the users knows that there's a  
PowerPoint file and a PDF and that they are claimed to be "equivalent".

The user but not the browser can probably guess that the PowerPoint  
file is the master file and the PDF was generated from it. Also, the  
user may be able to guess that opening the PDF will more likely to  
retain fonts and formatting than opening to OpenOffice.org with a  
different set of available fonts than what the author had.

Now, if instead of the fancy markup there was this
<p>Presentation Foo Bar is available as a <a  
href="foobar.ppt">PowerPoint file</a> and as a <a  
the user would neither better nor worse off it were still the user  
who had to make the choice. Chances are that in both cases the user  
would pick PDF.

But what if the page said this
<p>Presentation Foo Bar is available as a <a  
href="foobar.ppt">PowerPoint file</a> and as a <a  
href="foobar.pdf">PDF without animations</a>.</p>

Now the user can (without much pondering) figure out that the author  
thought animations were worth mentioning and the PDF file doesn't  
have those. Now the user could instead pick the PowerPoint file and  
risk font breakage and slight layout quirks in order to see animations.

What would the browser pick and why?

>> I would assume that editing some invisible metadata is a bigger
>> hurdle than writing text and making a plain link.
> There's that incomprehensible use of "invisible metadata" again :)  
> When we're
> talking about authors, prose and markup are equally visible.

Only to authors who use a text editor and look at their own markup  
source. With other kinds of editors even if the editor had UI for  
"invisible metadata", chances are it wouldn't be equally visible to  
prose and plain links.

> I can't follow. I'm not talking about browsers being smart. I'm  
> talking about
> users making decisions that suit them best.

I thought above you were talking about browsers making decisions for  
users by default and the users having a recourse to correct these  

> [2] An indexing bot can see that 'invisible metadata' conflicts  
> with 'visible
> prose' and decide to therefore ignore the visible prose. (When the  
> visible
> prose of a page is about turtles, and the invisible metadata about  
> porn, for
> instance.)

If software were smart enough to figure out whether explicit  
assertions are lies, why bother with making explicit assertions in  
the first place instead of letting the software do its smart thing?

Henri Sivonen
Received on Friday, 3 August 2007 09:28:36 UTC

This archive was generated by hypermail 2.3.1 : Thursday, 29 October 2015 10:15:25 UTC