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Your comments on WCAG 2.0 Last Call Draft of April 2006

From: Loretta Guarino Reid <lorettaguarino@google.com>
Date: Thu, 17 May 2007 16:38:49 -0700
Message-ID: <824e742c0705171638w242213e0ib1a5cf23d01670bf@mail.gmail.com>
To: "Kiyochika Nakamura" <nakamura-kiyochika@mitsue.co.jp>
Cc: public-comments-WCAG20@w3.org

Dear Kiyochika Nakamura ,

Thank you for your comments on the 2006 Last Call Working Draft of the
Web Content Accessibility Guidelines 2.0 (WCAG 2.0
http://www.w3.org/TR/2006/WD-WCAG20-20060427/). We appreciate the
interest that you have taken in these guidelines.

We apologize for the delay in getting back to you. We received many
constructive comments, and sometimes addressing one issue would cause
us to revise wording covered by an earlier issue. We therefore waited
until all comments had been addressed before responding to commenters.

This message contains the comments you submitted and the resolutions
to your comments. Each comment includes a link to the archived copy of
your original comment on
http://lists.w3.org/Archives/Public/public-comments-wcag20/, and may
also include links to the relevant changes in the updated WCAG 2.0
Public Working Draft at http://www.w3.org/TR/2007/WD-WCAG20-20070517/.

PLEASE REVIEW the decisions  for the following comments and reply to
us by 7 June at public-comments-WCAG20@w3.org to say whether you are
satisfied with the decision taken. Note that this list is publicly

We also welcome your comments on the rest of the updated WCAG 2.0
Public Working Draft by 29 June 2007. We have revised the guidelines
and the accompanying documents substantially. A detailed summary of
issues, revisions, and rationales for changes is at
http://www.w3.org/WAI/GL/2007/05/change-summary.html . Please see
http://www.w3.org/WAI/ for more information about the current review.

Thank you,

Loretta Guarino Reid, WCAG WG Co-Chair
Gregg Vanderheiden, WCAG WG Co-Chair
Michael Cooper, WCAG WG Staff Contact

On behalf of the WCAG Working Group

Comment 1:

Source: http://www.w3.org/mid/449A8F1D.5080403@mitsue.co.jp
(Issue ID: LC-1234)

Comment: This success criterion should be Level 1 because if it isn't
satisfied, information could not be conveyed, at least for screen
reader users. In the conformance section, a minimum level of
accessibility is defined as a level 1 success criteria. Without this
criterion, some important information might be conveyed to some users.
So, I believe it is essential to achieve a minimum level of

Proposed Change:

Move this success criterion to level 1.

Response from Working Group:

Success criterion 1.3.4 has been combined with success criterion 1.3.1
at level A. SC 1.3.1 now reads:

Information and relationships conveyed through presentation can be
programmatically determined or are available in text, and notification
of changes to these is available to user agents, including assistive

Comment 2:

Source: http://www.w3.org/mid/449A8F1D.5080403@mitsue.co.jp
(Issue ID: LC-1235)

Comment: Is there any scientific or other basis for a luminosity
contrast ratio method? Also, is there any reason to choose 5:1 and
10:1? I understand that a reference value is needed for these criteria
because it should be testable, but if there is no basis, how can we
rely on it?

Proposed Change:

Add a link to the document which explains why 5:1 and 10:1 LCR ratio
are sufficient if there is such a document. Otherwise, explain why the
WG has decided to choose 5:1 and 10:1.

Response from Working Group:

The 5:1 contrast ratio provides a minimum contrast of around 3:1 for
the major types of color blindness. A contrast ratio of 3:1 is the
minimum level recommended by ANSI/HFS 100-1988. 10:1 provides
approximately 7:1 contrast ratio for individuals with color blindness,
which is the recommended contrast level in ANSI/HFS 100-1988.

We have added the following to the Intent sections of SC 1.4.1 and 1.4.4:

The 5:1 contrast ratio provides a minimum contrast of around 3:1 for
the major types of color blindness. A contrast ratio of 3:1 is the
minimum level recommended by [ISO-9241-3] and [ANSI-HFES-100-1988].

Calculations in ISO 9241-3 and ANSI/HFS 100-1988 are for body text. A
relaxed contrast ratio is provided for text that is much larger (twice
as tall and with three time the thickness of lines in the character).

Notes on formula

Conversion from nonlinear to linear RGB values is based on IEC/4WD
61966-2-1 [IEC-4WD] and on "A Standard Default Color Space for the
Internet - sRGB" [sRGB].

The formula (L1/L2) for contrast is based on ISO 9241-3 and ANSI/HFS
100-1988 standards.

The ANSI/HFS 100-1988 standard calls for the contribution from ambient
light to be included in the calculation of L1 and L2. The .05 value
used is based on Typical Viewing Flare from IEC/4WD 61966-2-1 and the
sRGB paper by M. Stokes et al.

This success criterion and its definitions uses the terms contrast
ratio and relative luminance rather than luminance to reflect the fact
that Web content does not emit light itself. The contrast ratio gives
a measure of the relative luminance that would result when displayed.
(Because it is a ratio, it is dimensionless.)

Note: Refer to related resources for a list of tools that utilize the
contrast ratio to analyze the contrast of Web content.

Comment 3:

Source: http://www.w3.org/mid/449A8F1D.5080403@mitsue.co.jp
(Issue ID: LC-1236)

Comment: Is there any basis for saying that a 20 decibel difference is
good enough? How do I explain to our customers when they ask why it
requires a 20 decibel difference? I think "just because WCAG 2.0
states" is not a sufficient answer.

Proposed Change:

Add a note or any kind of explanation which states the reason why a 20
decibel difference has been chosen.

Response from Working Group:

There are a number of studies that this is based on. One is the Report
done for the Access Board in 1999. In that study, 75% of the subjects
needed a S/N of 18 dB to be minimally acceptable.

The most recent is Interference in Hearing Aids from Digital Wireless
Telephones by Levitt, Kozma-Spytek, and Harkins in Seminars in
Hearing/Volume 26, Number 2, 2005. It found that a signal to noise
ratio of 32 to 28 db was needed for 90% to find phones highly usable,
24 to 20 db for 90% to for minor limitation on use and 15 to 12 db for
Major Limitation of use.

Comment 4:

Source: http://www.w3.org/mid/449A8F1D.5080403@mitsue.co.jp
(Issue ID: LC-1237)

Comment: This success criterion should be Level 1 because, for
example, if it isn't satisfied and background audio interferes screen
readers, information could not be conveyed. Also, even if a mechanism
to turn off background audio is provided, some users could not find
the mechanism because of its background audio, so it would be better
that the success criterion itself was reconsidered.

Proposed Change:

Move this success criterion to level 1. And possibly restates the
criterion such that "do not play background audio without user

Response from Working Group:

Because automatic audio can interfere with assistive technology, SC
1.4.1 (formerly 1.4.2) has been moved to level A.

Comment 5:

Source: http://www.w3.org/mid/449A8F1D.5080403@mitsue.co.jp
(Issue ID: LC-1238)

Comment: Why this criterion allows the time-out which is not essential
for its function? If the first three list items of the criteria are
allowed, some users might not be able to read through the content. For
example, when the function to deactivate the time-out is provided but
it is placed on the end of the page, then some users cannot reach the
function before the time-out.

Proposed Change:

Omit the first three list items from this criterion.

Response from Working Group:

Providing a mechanism to update a time-out that the user may not
encounter before the time-out expires would not meet the requirements
of this SC. We have revised SC 2.2.1 to clarify this:

2.2.1 Timing: For each time limit that is set by the content , at
least one of the following is true:
    * Deactivate: the user is allowed to deactivate the time limit
before encountering it; or
    * Adjust: the user is allowed to adjust the time limit before
encountering it over a wide range that is at least ten times the
length of the default setting; or
    * Extend: the user is warned before time expires and given at
least 20 seconds to extend the time limit with a simple action (for
example, "hit any key"), and the user is allowed to extend the time
limit at least ten times; or
    * Real-time Exception: the time limit is a required part of a
real-time event (for example, an auction), and no alternative to the
time limit is possible; or
    * Essential Exception: the time limit is part of an activity where
timing is essential (for example, competitive gaming or time-based
testing) and time limits can not be extended further without
invalidating the activity.

Comment 6:

Source: http://www.w3.org/mid/449A8F1D.5080403@mitsue.co.jp
(Issue ID: LC-1239)

Comment: The term, "parsed unambiguously," or "parsed into only one
data structure" is not good enough to comply with the principle 4. The
principle states that "content should be robust enough to work with
current and future user agents." Then, if web units or authored
components are well-formed but include information not based on chosen
technologies, can we guarantee that this information is conveyed?
Therefore, I believe if forward compatibility is important,
"conforming to specifications" would be better than "parsed

Proposed Change:

Using the phrase "conforming to specifications" instead of the phrase
"parsed unambiguously."

Response from Working Group:

The working group looked at this topic carefully over an extended
period of time and concluded that requiring strict adherence to all
aspects of specifications does not necessarily result in an increase
in accessibility. For example, it is possible to create invalid pages
that present no accessibility barriers. It is also possible in certain
situations to enhance accessibility through the use of markup that is
not part of the specification.

The working group must work within its charter and only include things
that directly affected accessibility. Some aspects of "use
technologies according to specification" and validity do relate to
accessibility. However, others do not. So requiring validity would
take us beyond our charter. We do recommend it though and it is our #1
technique listed for conforming to SC 4.1.1.

Comment 7:

Source: http://www.w3.org/mid/449A8F1D.5080403@mitsue.co.jp
(Issue ID: LC-1240)

Comment: In example 3, the Japanese phrase after the round bracket,
"どうすることもできなくなり、あきらめること", is the meaning of the phrase "さじを投げる".
Therefore, it doesn't need to be inserted here. Also, this Japanese
expression is a present form. So, either changing the Japanese phrase
into past tense or the English sentense into present form is needed.

Proposed Change:

Remove the characters between the round bracket and the closing double
quotation mark (including the round bracket.) Then, either change
"さじを投げる" into "さじを投げた", or English verbs into past forms.

Response from Working Group:

Thank you for pointing this out. We've deleted the explanation in
parenthesis and have fixed some grammatical errors in the example
based on other comments. The example now reads, "Example 3: In
Japanese, the phrase "さじを投げる" literally translates into "he throws a
spoon". But it means that there is nothing he can do and finally he
gives up."
Received on Thursday, 17 May 2007 23:39:09 UTC

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