Add an atom:category element to both atom:head and atom:entry. It can appear multiple times. It is straightforwardly modeled on the RSS2 category element.
Withdrawn in favor of PaceCategoryRevised
Looking at RSS2, the only element which it provides that is actually widely used but doesn't yet appear in the Atom feed format is "category".
Add new sections 3.7, 4.2.13, and 5.13 to the atompub-format-03 draft.
==== 3.7 The Category Construct ==== The atom:category element contains information about a category to which an Atom feed or entry is associated. It has one attribute, "domain", which is a URI that identifies a categorization scheme. Its textual content should be a multi-part string, with the parts separated by slash ("/") characters, identifying a taxonomic category.
==== 4.2.13 The "atom:category" element ==== A Category Construct identifying a category to which the feed is associated. atom:head elements MAY contain any number of atom:category elements.
==== 5.13 The "atom:category" element ==== A Category Construct identifying a category to which the entry is associated. atom:entry elements MAY contain any number of atom:category elements.