Re: Marking up alternative versions of content

On Aug 3, 2007, at 10:06 PM, Robert Burns wrote:

> The @type attribute is not always a MIME type. The INPUT and BUTTON  
> elements both have types that are not MIME types, but simple  
> classifications just like this proposal. Though deprecated, LI, OL  
> and UL all had @type attributes unrelated to MIME type, but rather  
> classification types. Despite being deprecated fo some of these,  
> the point  is there is plenty of historical precedent in HTML for  
> non-MIME type @type attributes. As for distinguishing between  
> different equivalent types, I think a @type attribute would be good  
> (we could also have @contenttype to provide two different ways to  
> classify the element). Also we have the @title attribute available  
> on the ALT element to provide human-readable information about the  
> differences.
>
> I had earlier suggested a LONGDESC element (ALT, EQUIV, FALLBACK or  
> LONGDESC all work for me). At least for a one-to-one relation, to  
> me it makes more sense to use the @lkongdesc attribute from the  
> original element. To go from primary ---URL---> fallback rather  
> than referencing from fallback ---IDREF---> primary. Multiple  
> equivalents could be handled by letting ALT have a content model  
> that includes an initial ALT or adding a @longdesc attribute to ALT  
> too. Advantages of this approach include:
>
>  • @longdesc is already supported (backwards compatible)
>  • @longdesc as a URL instead of an IDREF permits greater author  
> flexibility (to optimize bandwidth usage and the like) by pointing  
> @longdesc to either a local '#idref' URL or a remote document URL
>  • authors can (I guess have to in some sense) express a ranked  
> preference for equivalents that users and UAs can take into  
> consideration.

One other thing I meant to suggest on this, is that the ALT element  
could act like a SWITCH (in SVG for example). So an FaLLBACK element  
(instead of ALT) would contain multiple ALT elements. This way it  
would be a simple hierarchy between the primary document contents and  
the alternates. Each ALT could possibly have a @type, a @contenttype  
and a @title to help a UA and a user select from among the  
alternates. This FALLBACK element could even be used within an OBJECT  
element to change the fallback from a hierarchically arranged  
fallback into shallow hierarchy separating the primary from the  
alternates.

Take care,
Rob