Some issues include:
- what domain to use? Candidates include:
- what about versioning? how to keep in sync with the wiki and test materials?
- what profile URI to use for combinations, such as hCard 1.0 and hCalendar 1.0?
- note HTML4.01 states "that one or more meta data profiles, [are] separated by white space." Though it's simpler for authors if they can just use one profile URI.
- More profiles are needed.
One proposal is: use www.w3.org, following W3C namespace policy. As to versioning, change the profile whenever the wiki changes (within some reasonable latency, say, a couple weeks or a month). For example: an hCard Profile at w3.org, and discussion: an hCard profile that seems to work with GRDDL.