My poking around in the world of RSS has inevitably led me to OPML, another XML format created by Dave Winer, and is ostensibly designed to contain outline-structured information. What is outline-structured information? A fancy way of saying a structured list of hierarchical content, like browser favorites or web directories like Yahoo. It seems any list will do, actually.

I’m interested by what I see, but I’m still reserving judgment. It looks like OPML will be/is valuable in the same space as RSS (e.g. weblogs), but I can’t find a concrete description of the specification (so far, at least) beyond version 1.0—yet I keep finding OPML files online referring to themselves as version 1.1, and each one has a slightly different set of attributes. Is there a 1.1 spec? Or is it only proposed, letting content creators add features willy-nilly? Hmmm.