alertdialog versus dialog questions, also modal versus non-modal

Apologies if this question has already been discussed, but I fail to  
see a meaningful difference in the ARIA roles for alertdialog and  
dialog. AFAIK, the only discussion of this on the xTech list is the  
following, where Al points out an implementation problem with  
@role="alert dialog"

http://lists.w3.org/Archives/Public/wai-xtech/2008Apr/0028.html

Implementation issues aside, it seems to me that there is no  
meaningful difference between an alert dialog and a standard dialog.  
Both roles use an application window that receives focus and requires  
some form of user input or acknowledgment. If this is true, they  
should both be standard dialogs, because @role="dialog" appears to be  
just a child role of @role="alert" that also receives focus. Please  
correct me if I'm missing something in the reading or implementation.

For reference:

alertdialog <http://www.w3.org/TR/wai-aria/#alertdialog>
	A separate window (may be simulated) with an alert, where initial
	focus goes to the window or a control within it.

dialog <http://www.w3.org/TR/wai-aria/#dialog>
	A dialog is a small application window that sits above the application
	and is designed to interrupt the current processing of an application
	in order to prompt the user to enter information or require a response.

The other bit that's not clear from this wording is how to achieve a  
modal versus non-modal dialog. Since dialog is "designed to interrupt  
the current processing of an application," I assume that means it  
maintains a "modal" state and intercepts all input until it is  
dismissed. Have I missed some other allowance for non-modal dialogs?

Thanks,
James Craig

Received on Tuesday, 27 May 2008 23:32:52 UTC