Proper use of labelledby vs describedby and definitions

Hi!

I am struggling with how to best handle annotating definitions (and
references to those definitions) in a document.  There are two classes:


   1. Terms that are defined in a definition list.  It seems obvious that
   the content of a dt element would have a role of definition, and it should
   use aria-describedby to refer to its corresponding dd element.  I know the
   spec says to use aria-labelledby, but that doesn't really make sense if the
   content of the dd element is very long (right?).
   2. Terms that are defined inline.  Consider an example:

   <p>A paragraph about the term <dfn>theterm</dfn> that describes a lot of
   stuff about that term.</p>

   I think that the dfn gets a role of "definition" - but do we use
   aria-describedby? If so, is the description the entire paragraph?


Also, when referencing a defined term elsewhere, should we also use
describedby and point back to the terms description?  E.g., <p>I have some
content where I am talking about <span class="internalDFN"
aria-describedby="someID">theterm</span> and relating it to other
things.</p>

Thoughts?

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