ISMAP-class problem with script

Chuck described a problem event-handling script for us in the
User Agent telecon a week or so ago.  As I understood the 
scenario, it is "the same class of object as the deprecated
server-side sensitive image map."

I want to build on this analogy in our WAI-PF dialog with the
DOM group about accessibility requirements.  But I owe the
example to Chuck and that meeting, so I am writing it down
here first.

There is a table.  in the table cells there are images.  There is
no on-mouse-down event handler bound to any of the images, but
there is one on the table.  The script which handles
on-mouse-down for the table, however, inspects the current mouse
location to decide what to do.

To perfect the ISMAP analogy, let us just say that it compares
the mouse position with a disjoint set of rectangles falling
entirely within the table and each one completely enclosing one
image.  This is a control morphology identical to a sensitive
map.  Now, we have established accessibility standards that say a
sensitive map should be done on the user side because then the
user agent can give the user verbal information about the
available control actions and their prospective outcomes.  In a
sense, the DOM question is "Is the DOM a frame of reference where
we can recognize that this is the same thing as the server-side
image map pathology?"

Jon has done a good job in his note about "DHTML Issues"
that this is the basic usability/accessibility problem:
how can the user have adequate visibility over the potential
consequences of actions so that the UI merits being rated
as "exhibiting predictable response?"

To the user, the on-mouse-down handler is a method associated
with an object, the table.  I suspect that DOM 1 only covers the
information associated with the table that the HTML tells us, not
the behavior of its methods that the script tells us.

When and how to get the model to cover and discipline what
actually bites the user is one of the things that WAI-PF
and the DOM WG need to discuss.

Al

Received on Saturday, 3 October 1998 15:39:13 UTC