I think the this/that/the-other usage is well-enough established now to qualify as prior art. Anyhow, if you want to have your own not-hierarchical categorization scheme, you can, just keep it in your own namespace. You can even put it inside atom:category. -Tim
FWIW, the protocol design team came out pretty firmly against the idea of enforcing a hierarchy on categories (categories-as-discoverable-protocol-items, that is). DAGs were thought to be a realistic use-case, and maybe other non-hierarchical structures, too.
If a category element is needed in the feed format, let's not impose any relationships between them. What use could it have? If there are existing schemes that are hierarchical, then consumers can make use of that meaning.
Imposing semantics on the slash character within the human-readable category name could have problems. Consider my (flat) category scheme for life:
Animals Plants Fungi Protozoa/Monera
When it comes to single-celled buggers, I'm not very discriminating.
Ezra
