In my latest post, I mentioned that I really view tags and categories as two facets of the same thing.  Turns out I'm not alone.

This interesting post explains how WordPress implements tags and categories.  Like me, it's apparent that they view both tags and categories ultimately as the same entity type: "terms".  They then overlay a set of structures that enable various use of "terms" in the WP UI.

I think a similar - if not identical - approach should form the basis of tagging and categorization in the DNN blog module.