W3C home > Mailing lists > Public > w3c-wai-ua@w3.org > October to December 2000

RE: Equivalent issue

From: Hansen, Eric <ehansen@ets.org>
Date: Wed, 08 Nov 2000 18:08:49 -0500
To: "'Jon Gunderson'" <jongund@ux1.cso.uiuc.edu>, w3c-wai-ua@w3.org
Message-id: <B49B36B1086DD41187DC000077893CFB8B451F@rosnt46.ets.org>
I am preparing a material on "Equivalency" that will, I think, include a
section on Frequently Asked Questions. I think that might help clarify

My comments are marked with "EH:"

> -----Original Message-----
> From: Jon Gunderson [mailto:jongund@ux1.cso.uiuc.edu]
> Sent: Wednesday, November 08, 2000 1:37 PM
> To: w3c-wai-ua@w3.org
> Subject: Equivalent issue
> This is a summary from what I have seen on this issue:
> 1. The term "Primary" content used in WCAG 1.0
> Concerns raised:
> a. The term "primary" implies that some content is not considered as 
> important as other content
> Proposal: To use the term "equivalency target". 

EH: I think that the term 'equivalency target' is much simpler, cleaner, and
certainly better defined than the term 'primary content'.

> definition is based on 
> a user, rather than an author perspective.  A user can select 
> an equivalent 
> for any element that is not usable by them.  The element that 
> is not usable 
> to them is referenced as the "equivalency target" of the 
> equivalent they 
> select for rendering.  The author therefore does not 
> necessarily need to 
> consider the term "equivalency target" in the equivalents 
> that they prepare 
> for elements in their document.

EH: I think that I would phrase it otherwise. WCAG 1.0 requires text
equivalents for all non-text elements that is authored. In order to fulfill
this requirement, each author-provided non-text element must take the role
of an 'equivalency target' for which the text equivalent is the
'equivalent'. So each multimedia presentation, audio-only presentation, and
video-only presentation, image, etc., becomes an equivalency target for
which the content developer is to provide a text equivalent (as the
'equivalent'). UAAG 1.0 is required to render 'all content' and also to
ensure that there is a text equivalent for each user-agent-generated message
that is non-text content. Some day, the user him or herself might be able to
say, "Here is a non-text element that that I cannot understand. The author
did not provide a text equivalent. User Agent, generate me a text equivalent
for it so that I can understand it." The User Agent might then use a
combination of picture recognition, voice recognition, or other technologies
to produce a text equivalent (or some other kind of equivalent) based on
these user-specified 'equivalency targets'. But that is beyond the scope of
our current document.

> 2. How equivalent are "Equivalents"
> The terms used used to discuss this issue include asymmetrical and 
> symmetrical relationships between equivalents.  There has also been 
> discussion of mathematical relationships for equivalency.  
> Some people seem 
> to want to require some type of "mathematical" equivalency 
> for equivalents 
> or at least have authors view equivalents as equally usable by people 
> without disabilities to get the same information.
> Proposal:  This is really a WCAG issue and this is where this type of 
> definition needs to be made.  UAAG can only deal with 
> equivalents that can 
> be recognized in markup and offer those for rendering to the 
> user.  The 
> user agent cannot test and therefore guarantee that any recognized 
> equivalents actually provide the same information to the user.
> Has anyone raised this with WCAG?

EH: I am in favor of not doing things in UAAG 1.0 that would necessitate
significant changes in WCAG 1.0, notably the definition of 'Equivalent' and
the wording of WCAG 1.0 checkpoint 1.1. I have not raised these issues with

> 3.
> Jon Gunderson, Ph.D., ATP
> Coordinator of Assistive Communication and Information Technology
> Division of Rehabilitation - Education Services
> MC-574
> College of Applied Life Studies
> University of Illinois at Urbana/Champaign
> 1207 S. Oak Street, Champaign, IL  61820
> Voice: (217) 244-5870
> Fax: (217) 333-0248
> E-mail: jongund@uiuc.edu
> WWW: http://www.staff.uiuc.edu/~jongund
> WWW: http://www.w3.org/wai/ua
Received on Wednesday, 8 November 2000 18:09:00 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 January 2015 14:49:28 UTC