"Vancouver" is just a string of letters that have meaning to humans, in my case when tagging content on my blog, the city of Vancouver. Machines don't know this for sure, however, and for any future machine to come along and do something meaningful with the content on justagwailo.com/tag/vancouver as it pertains to the city of Vancouver, British Columbia, I will need to 'machine tag' the Drupal taxonomy term with a URL identifying it unambiguously as referring to the city. The links below propose an RDFa solution to this, though there is no module to automatically mark up the HTML in RDFa.
Drupal issue: Add a concept URI field to taxonomy terms http://drupal.org/node/490916
Extend the Taxonomy module
Add a field for the URL
Below the Description field?
On the tag page itself:
Can it integrate with the RDF module? Will need to add the namespace to the body tag of the taxonomy term page.
Surrounding the tagged node:
multiple Common Tags for the entire document?
multiple Common Tags for just the node content?
Taxonomy term page example (in progress):
<body class="page page-taxonomy page-taxonomy-term page-taxonomy-term-1">
Bits in red would be added by the Common Tag module.
Node example (in progress):
<div id="node node-321"> <!-- created by the theme's node.tpl.php -->
[Content about baseball here.]
<ul xmlns="http://commontag.org/ns#" rel="ctag:tagged" about="#node-321" class="links inline"><li class="taxonomy_term_1 first last active"><a rel="tag" typeof="ctag:Tag" rel="ctag:means" href="http://en.wikipedia.org/wiki/Umpire_(baseball)">Umpires</a></li></ul>
</div> <!-- /terms -->
</div> <!-- /node -->