In Atom, categories have schemes. What scheme should we use for tags?
categories are pretty obviously the same thing, although some
existing publishing systems store and handle them separately. Categories are
often apt to be hierarchical, tags never (that I know of).
Atom feed, both are
represented by the
category element. For example,
this article is in the category “Technology/Web”, so the Atom feed
<category scheme='http://www.tbray.org/ongoing/What/' term='Technology/Web' />
Suppose I wanted to tag it, uh, “Tagging”. What value should I supply for
scheme? Just leave it blank? (Atom allows that.) Or maybe
nthere should be a well-known scheme value saying “This is one of those, you
Miscellaneous, folksonomy, tagsonomy, groovy ‘Tag’ thingies, not a boring
fusty old hierarchical ‘category’.”
This is one of the few situations in which I can imagine being comfortable
with a URN, and looking at the
Registry reveals that
urn:tag isn’t used. Should I write an
Internet Draft and register it? Then my Atom feed could have:
<category scheme='urn:tag' term='Tagging' />
Or is there an obviously-better idea?
[Update: I whipped up a urn:tag I-D.] [Lots of intelligent points raised in the comments; I dropped one in to address them. I still think this is a good idea.]