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[Summary] DOM / UA / Event issues for today's meeting

From: Ian B. Jacobs <ij@w3.org>
Date: Thu, 20 Dec 2001 12:43:59 -0500
Message-ID: <3C22235F.76DA9273@w3.org>
To: w3c-wai-ua@w3.org, plh@w3.org, asgilman@iamdigex.net, jongund@uiuc.edu, rayw@netscape.com
CC: www-dom@w3.org
Hello,

To prepare for today's meeting on DOM events and requirements for
accessibility, I've summarized where I think we are. Please let
me know what I've missed so that we are sure to address the
key points at the meeting.

The two main points seem to be the following:

1) What's the best way to ensure that assistive technologies
   can identify and trigger event handlers?

2) What's the best place to describe the semantics of
   author-specified behaviors?

------------------
1) What's the best way to ensure that assistive technologies
   can identify and trigger event handlers?
------------------

Goal: When the author makes available a functionality that is
available with one input device, provide access to that
functionality via another input device. 

Event types are generally defined in a format (e.g., onMouseDown,
onFocus, etc.). A given node may have zero or more listeners
(i.e., programs) associated with a given event type.

From what I understand, DOM 2 allows programs to dispatch an
event of a given type to a node. DOM 2 does not allow
per-listener activation, but I don't think that's an
accessibility requirement. So the dispatch solution seems to
suffice.

DOM 2 does not allow programs to query a node to know whether
there are event handlers of a given type associated with the
node. The UAWG initially asked that the DOM WG solve this by
making the list of listeners available.  The DOM WG replied that
there is a better solution: a boolean function that returns true
or false depending on whether a node has handlers of a given
type. So the query solution seems to suffice.

Have we converged? What's missing in terms of query and
activation?

------------------
2) What's the best place to describe the semantics of
   author-specified behaviors?
------------------

Point one is about device-independent access. Point two is about
user interface.

Goal: Provide the users with clues about expected behavior when
the user does not have access to the usual clues of the "primary"
output mode.

Use case: The mouse user drags the mouse over a piece of screen
and a visual-only cue suggests that, by clicking, the user will
have access to another page of information. What's a good way to
let the non-visual/non-mouse user know to "click here"?

There have been suggestions that formats should allow authors to
describe behavior in markup. Imagine the following use case:

 * The user moves focus to an enabled piece of content.
 * The assistive technology queries the node and learns that
   there are onMouseOver and onMouseDown event handlers associated.
 * Either the user queries the content or the AT informs the
   user automatically that interaction is possible. 
 * The user queries the content for the author-specified
   description of what is expected to happen on activation. 
   Based on that information, the user makes a decision.

There have been discussions about whether the author should
describe behavior at the event level or at a higher semantic
level.  I think this is a topic where more discussion is
required: how should formats let authors describe available
behaviors? This is a format question more than a DOM question.

 - Ian


-- 
Ian Jacobs (ij@w3.org)   http://www.w3.org/People/Jacobs
Tel:                     +1 718 260-9447
Received on Thursday, 20 December 2001 12:44:04 GMT

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