Many blogs use the concept of "tags" and "categories" to add metadata to a post. What is the best practice for semantic markup for this information, such that a machine reading the blog post could easily identify the tags?

Currently I add "tag" to the rel attribute on the link, e.g.

<a rel="tag" class="tag" href="/tags.html#site-configuration">#site-configuration</a>

I suppose one could use Dublin Core's html format for keyword:

<meta name = "DC.Subject"
          content = "site-configuration">

and add this to the page header, or can meta tags go in the body? Is one or the other preferable, or some entirely different option?

Is there a better strategy in terms of providing precise and standardized definitions for content?

Is HTML5 a reasonable choice if I want to be so picky about metadata, or should I be using an XML doctype?

What are the pros and cons of the different approaches?

xml html metadata schema.org
Edit
Report