There's a lot of talk about what we will do with RDA as data - what format we will use, how it will look to users, etc etc etc. In fact, the options are legion. The key point is that we don't have to decide on just ONE WAY to carry and store RDA data elements, as long as we follow a few rules.
As an experiment, I have coded a very simple bibliographic record using two different possible ways to encode RDA in XML. For the XML data elements I use the RDA elements from the Open Metadata Registry. These elements are defined in OWL, and therefore are compatible with semantic web applications. Their use in XML (and by that I mean non-RDF XML) may be a bit questionable, yet at the same time XML may be a good transition format from our current data to a ful RDF-based implementation. I created two XML files: one in which I used text values, much as one would in MARC, and one in which I used URIs for values that have been encoded as vocabularies. Neither has a schema because creating a schema for RDA is a huge undertaking. If there is interest in this method, however, it might be worth... undertaking.
The resulting files don't fit well in a blog post, so I created a page with a side-by-side comparison. Please have a look. Feel free to comment or send me suggestions or corrections. or other ideas on how to do this better.