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Re: WCAG-CSS mapping part 1

From: Wendy A Chisholm <wendy@w3.org>
Date: Fri, 19 Dec 2003 12:55:36 -0500
Message-Id: <>
To: Tim Boland <frederick.boland@nist.gov>, w3c-wai-gl@w3.org


These three files are a great start. Thank you.  It would be helpful if 
there were links to guidelines, success criteria, and modules.

Tim wrote:
>  It may not be possible
>to satisfy all WCAG success criteria just by using CSS techniques.

We have not been assuming that someone could use CSS alone to satisfy all 
of the success criteria.  Since CSS is used in conjunction with other 
technologies, we have discussed marking the dependencies between techniques 
(in our xml source) so that we can generate checklists that will pull 
together the various technology-specific pieces that someone might 
need.  Client-side scripting is also a "supporting" technology rather than 
a "host" technology.  It will not be possible to meet all success criteria 
using only a supporting technology.

This intent is documented in  the "Scope of Documents" section of 
"Requirements for WCAG 2.0 Checklists and Techniques" [1]

Note: the Requirements document needs to be updated to reflect changes in 
terminology (for example, what used to be called "Checkpoints" are now 
called "Guidelines").

[1] <http://www.w3.org/TR/wcag2-tech-req/#scope>

>(1) to what extent is it possible (or feasible-practicable) to satisfy the 
>various WCAG conformance levels by just using
>CSS as a supporting technology (applied to HTML, or to XML, or to SVG, or 
>to something else)?

If I understand correctly, this question is about satisfying Level 1 
success criteria vs Level 2 success criteria by opting to use CSS.  In 
other words, if I am using CSS to do X, do I automatically meet any success 

By thoroughly using CSS (with HTML), I think an author could almost 
automatically satisfy Guideline 1.3 (Information, functionality, and 
structure are separable from presentation).  (To get discussion started, 
I'm only considering HTML+CSS, and not other combinations of technologies, 
in the following examples)

Using CSS will not likely effect conformance with Guidelines 1.1 (text 
equivalents or descriptions) or 1.2 (equivalents for multimedia).

Depending on the language (and our interpretation of the Guideline), 
"Guideline 1.4 All text can be decoded into words represented in Unicode" 
might be more easily met if CSS is used.

"Guideline 1.5 Structure has been made perceivable through presentation." 
will be more easily met if CSS is used.  As long as structural elements are 
used properly, the default presentation (for HTML) will make the structure 

Looking at the other guidelines, I think 1.3 is most directly tied with CSS 
(and separation of content from presentation).

>  What is
>a "minimum" combination of technologies that is needed for such satisfaction?

It depends on the technologies and how they are used.  It is possible 
(although not recommended) to create an accessible site solely with 
HTML.  Is this what you are asking or is there more to this question?

>(2) what does it mean for a CSS technique to have a significant or 
>material influence in satisfying
>WCAG success criteria, as opposed to just a tangential or assistive role 
>(with another technology
>being predominant)?

Could you provide more detail? I don't understand this question.

>Would it be better to organize WCAG success criteria in terms of degree of 
>CSS involvement?

Since we are writing WCAG to be technology-independent, I am unable to 
forsee how we would organize success criteria in terms of CSS. Instead, 
this would occur at the technology-specific level.  For example, the first 
Level 2 Success Criteria for Guideline 3.4 [2] "key orientation and 
navigational elements (such as navigation bars) are generally found in one 
or two consistent locations or their locations are otherwise predictable." 
There are a variety ways to satisfy this criterion. We ought to create 
an  HTML-specific technique that describes how to structure HTML and apply 
CSS (to the HTML) to create a navbar that appears at {position x,y} on 
{pages a-d} within a site.  Additionally we ought to write techniques 
describing server-side includes, templates, etc.  I also forsee overlap 
with ATAG 2.0 Techniques (e.g., for CMSs).

Does that make sense or do you have something else in mind?

[2] <http://www.w3.org/WAI/GL/WCAG20/#consistent-behavior>

>(3) If there is a choice of combinations of technologies that would 
>satisfy WCAG success criteria,
>which combination should be chosen? Since various CSS3 profiles are 
>expected to incorporate different
>combinations of CSS3 modules, implementing one CSS3 profile over another 
>may have implications as to
>also satisfying WCAG conformance levels.

CSS3 is in various stages of the W3C Recommendation track. I think we 
should focus first on CSS2 (and watch progress of the revised version: 
http://www.w3.org/TR/2003/WD-CSS21-20030915/).  We can include  "future 
techniques" but I think we ought to focus on what people can do today. An 
example of a future technique is in Section 9.5 "tabindex to skip link 
groups (future)" of HTML Techniques [3]

In the Guideline/success criteria layer we do not recommend specific 
combinations of technologies, but we encourage authors to choose 
technologies that have accessibility features and to use those 
features.  If they choose a technology that can not be used to make 
accessible content, then they must provide an alternative (Guideline 4.2 [4]).

However, at the Techniques layer, we can make technology-specific 
recommendations.  For example, in the latest Working Draft of HTML 
Techniques for WCAG 2.0 section 6.2 says, "Use style sheets to change list 
bullets." [5]

[3] <http://www.w3.org/TR/WCAG20-HTML-TECHS/#linkgroups_tabindex>
[4] <http://www.w3.org/WAI/GL/WCAG20/#technology-supports-access>
[5] <http://www.w3.org/TR/WCAG20-HTML-TECHS/#lists_style>

>(4) Is the content of a WCAG guideline "monolithic" with regards to 
>technologies needed to support that
>guideline? In other words, could I use different technologies to support 
>level 1 of Guideline X than I would use
>to support level 2 of Guideline X (importance of the levels vs. importance 
>of the guideline statement)?

Would the following be an example of what you are asking:
at Level 1: I use raster images to create cool text effects for navigation 
at Level 2: I convert my bitmaps to CSS to create the same cool text 
effects for navigation buttons

If this is similar to what you are asking, then no, this is not how the 
guidelines currently work.  Level 1 contains success criteria that do not 
require the author to change the presentation of content.  In the above 
example, the raster image and the CSS-defined text theoretically look the 
same therefore the presentation has not changed.

This is an interesting issue.  Previously I said that we can not recommend 
one technology over another, however I think we can recommend one technique 
over another.  For example, I think we can say "use text as text instead of 
images of text."   This could be applied across technologies:  use HTML/CSS 
instead of bitmaps, use structured PDF instead of a PDF image of text, etc.

This idea could be made clearer in "Guideline 1.3 Information, 
functionality, and structure are separable from presentation" (from 17 
November 2003 draft [6]).   I do not think that it is covered by the 
current success criteria, since the ability to programmatically determine 
relationships or emphasis is not the same as using text instead of bitmaps.

[6] <http://www.w3.org/WAI/GL/WCAG20/WD-WCAG20-20031117.html>

>Right now the document is just something to "shoot at", but is this a 
>possible direction for future development efforts?

The mapping is helpful.  The current format we are using for Techniques 
documents can be seen in HTML Techniques for WCAG 2.0 Working Draft [7].

Loretta took "CSS Techniques for WCAG 1.0" [8] and converted it to our 
techniques dtd.  I've been cleaning that up so that I can generate a 
document that is consistent with the HTMLTechniques.  XML source, XSLT, 
DTDs, and documentation are available [9].

[7] <http://www.w3.org/TR/WCAG20-HTML-TECHS/>
[8] <http://www.w3.org/WAI/GL/wcag20.html#techs>
[9] <http://www.w3.org/TR/2000/NOTE-WCAG10-CSS-TECHS-20000920/>

Thank you. Best,

wendy a chisholm
world wide web consortium
web accessibility initiative
Received on Friday, 19 December 2003 12:55:59 UTC

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