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Re: Why is WCAG 2.0 criterian 2.4.6. only leve AA?

for

From: Duff Johnson
Date: Apr 21, 2012 11:25AM

Birkir,

> I was doing a review of the WCAG, because I am commenting on an
> Icelandic adoption and description of the standard. And I came across
> something I did not notice before.
> SC criterian 2.4.6 (use descriptive headings and lables) is only level
> AA, not level A.

It's interesting that you ask this question - the subject is very much on my mind at this time.

2.4.6 is a content, not a technical prescription. It's an instruction on how to write, not how to semantically encode text. Level A appears generally reserved for "programmatically discernible" items (whether or not that's a good thing is another question).

I agree with you that 2.4.6 "feels" Level A, not AA. The way I prefer to read it goes like this:

"In cases where content is subdivided into logically distinct sections, then section headings/labels (if any) shall be "clear and descriptive" in order to meet the objectives implied by the Guideline."

Of course, as a practical matter, since almost all content does include headings, 2.4.6 is effectively Level A - at least in my mind.

What this raises, however, is the question of how it's possible to be "clear and descriptive" in headings without logic in the "structure" (an SC 1.3.1 Level A concept, hint hint) of headings.

For this reason, I don't understand why (or even how) 2.4.10 is broken out from 2.4.6.

Gosh, normative standards should be clearer than this! :-)

> Out of curious, does anyone know why this is?
> It seems a lot more fundamental to accessibility than a lot of the
> level A criteria I have come across, and it seems a bit out of
> character with the rest of the guidelines.
> Anyone got a historical or technical perspective on why this happened?

I wasn't there, so I can't help on the history. The technical context seems like HTML, in which structure and style are frequently mixed and in which long, deeply structured content is rare, and so, less considered.

I can, however, offer some context from the world of PDF.

In PDF logical structure there is no such question over "headings". In PDF, logical structure elements are unconnected with the appearance of content. If you use only 1 heading in a document and prefer an "H3 style" for it, no problem - but LOGICALLY that heading _is_ an H1 because ipso facto there's "no such thing" as an "H3 all by itself".

In PDF, subdivision headings are the primary and most effective means of content-based navigation for AT users. In part this is because heading structure elements in PDF are ONLY used for subdivisions of content - they have no other function (i.e., headings are not "importance" as they do in HTML 4).

Of course, not everyone authors their PDFs this way, but that's an education, not a technical problem.

One of the great advantages of PDF/UA is that conforming implementations will guide users towards better authoring practices simply because PDF/UA insists, normatively, on logical heading structures when headings are present.

Best regards,

Duff Johnson

President, NetCentric US
ISO 32000 Intl. Project Co-Leader, US Chair
ISO 14289 US Chair
PDF Association Vice-Chair

Office: +1 617 401 8140
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