more use case evaluations

Ian Hickson has posted new metadata use case evaluations at the WhatWG 
mailing list. I missed both at first, since I'm not subscribed to the 
group. Since these impact on the HTML WG effort, I'm posting links to 
both. I would also recommend that these items should be cc'd to both 
email lists. An echo effect is less harmful than silence, and a 
fragmented discussion is preferable to one that's a one-sided.

Exposing known data types in a reusable way 
http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-May/019833.html

Writing authoring tools and validators for custom microdata vocabularies 
http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-May/019839.html

Shelley