<resourceDesc>

While putting the finishing touches on the proposed language for #29, I came
across something I was not sure about. The definition of <resourceDesc> seems
a bit redundant with <mimeType>. I realize that <resourceDesc> is required, 
and <mimeType> is optional, but that is a minor tweak if we needed to change. 
Would it not be better to use <resourceDesc> as a human-readable description 
of the resource itself? Much like the alt attribute of the <img> element in 
HTML?

Thoughts?