Stephen Downes just posted 2 links that might be useful.
Latest issue of JIME. Topic is "The Educational Semantic Web". This is important because it may form a common way of describing resources in a more distributed way. APOLLO will need to tie into these concepts when they become available.
An article called "Improving Metadata Quality: Augmentation and Recombination" that talks about metadata as a collection of statements about a resource, and the possibility of managing metadata at the statement level. Sound familiar? APOLLO basically does this now.