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Structured HTML Precludes aria-posinset and aria-setsize?

From: Ben 'Cerbera' Millard <cerbera@projectcerbera.com>
Date: Fri, 28 Mar 2008 17:06:00 -0000
Message-ID: <001901c890f6$0113f9a0$0301a8c0@ben9xr3up2lv7v>
To: "Public PFWG" <public-pfwg-comments@w3.org>

Hello. Long time listener but first time caller. :-)

I've noticed the properties aria-setsize and aria-posinset mentioned by the 
ARIA Primer, section 6:

<http://www.w3.org/TR/2008/WD-wai-aria-primer-20080204/#businsessreasons>

If a tree is structured with the HTML elements for nested lists, namely <ul> 
and <li>, these attributes become redundant?

* setsize is available by counting the <li> at the current level.
* posinset is available by counting the <li> at the current level up to and 
including the current <li>.

The definitions seem to require this counting by UAs as a SHOULD:

* <http://www.w3.org/TR/2008/WD-wai-aria-20080204/#posinset>
* <http://www.w3.org/TR/2008/WD-wai-aria-20080204/#setsize>

If authors provide adequately structured HTML for controls such as this, 
perhaps they SHOULD NOT use aria-setsize and aria-posinset?

Encouraging authors to use properly structured HTML as the basis for their 
widgets is hinted at in the source order and nesting advice given by 
WAI-Aria Best Practices, section 2 "General Steps for Building an Accessible 
Widget with ARIA", step 3:

<http://www.w3.org/WAI/PF/aria-practices/#accessiblewidget>

Using good HTML as the basis would make the widget easier to manage 
dynamically. The script could move, add or remove the relevant elements 
without updating ARIA attributes. The UA would do the counting.

In the nested <ul> for treelist case, AT features for handling HTML lists 
would aid usability of the widget. Such as announcing the number of items at 
the start of each <ul> and saying "item x of y" for each <li>. A widget 
based on semantic HTML would natively support AT verbosity settings, so a 
user who preferred rapid progression through a document may hear "List" at 
each <ul> and a slight pause between each <li>.

I echo the sentiments of Henri Sivonen's message here:

<http://lists.w3.org/Archives/Public/public-pfwg-comments/2008JanMar/0045.html>

Perhaps some text along these lines could go somewhere:

"Where semantics and structures native to the host language exist and are 
adequate, widget authors MUST use them. For example, in HTML authors MUST 
use list elements as the basis for list-like form controls."

If this is already the advice, sorry but I missed it.

-- 
Ben 'Cerbera' Millard
Collections of Interesting Data Tables
<http://sitesurgeon.co.uk/tables/> 
Received on Friday, 28 March 2008 17:07:35 GMT

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